My Consumer unit, and outside power system

The way my installation has been done (not all by me!) is....
Live and Neutral enter my CU from my meter directly into a 80A RCD (MK model No LN 5780)
There is an earth wire coming out of the bottom of the electricity companies fuse box that runs to the CU (via a sealed (metal loops of wire with a lead like lump on) little box
I am in the process of trying to get the electricity board to come out and disconnect my main fuse so I can install a 100A isolator in between the meter and the CU, as I am intending wiring in a generator transfer switch (it's on the wall already!))
Off the 80A RCD are the following MCB's (nearest to furthest)
30A 30A 30A 20A 15A 10A
There is then some wire connected to the same terminals as the incoming supply (looks like 2.5mm) that then goes to the input of the lighting RCD (MK number 6730), this then has three 5A MCB's connected to it that supply all the lighting in the house.
(This is all in a single consumer unit)
My first question is, is this correct - I am concerned that the wires that run from the top (inlet) of the first RCD to the inlet of the second (lighting) RCD are not sufficiently protected (the only thing protecting them is the 80A electricity board fuse)
My next set of question start with....
There is a 15A MCB for the outside power - There is a 2.5mm T&E cable that runs from the CU to the workshop
It used to run to an old shed, but we have got a new one due to the fact it practically fell down! This old shed was supplied form the house via an overhead 2.5mm cable attached to a galvanised wire (this bit was about 5 meters)
The new workshop is slightly closer, so I have just moved the cable over to the new location - This overhead run is now about 4 Meters from the house to the workshop
In the old shed there was a crappy old fuse box - This has gone in the skip as it was rusty, and sometimes tripped the main RCD when it was switched off!
I have installed a new consumer unit in the new workshop
This has a 30mA RCD
The sockets in the workshop are connected to a 15A MCB
The lights in the workshop are connected to a 5A MCB
There is another shed right next to the workshop, this too has it's own 15A MCB for the sockets, and a 5A for the lights
The cables to the other shed are run through a length of green corrugated plastic pipe, remarkably similar to what NTL use from the tee in the road to the drop box ;) - As I said before, the shed is right next to the workshop, so the pipe is only about 15cms long!
There is then a 2.5mm T&E cable that runs from a 15A MCB in the workshop, through the other shed, then underground (in what looks like water pipe) to the garage at the top of the garden (about 25M away)
This currently has yet another CU with two fuses, one 15A for the sockets, and a 5A for the lights.
Then from this garage, wired into the 15A fuse (along with a socket in the garage), there is a 1.5mm T&E cable that runs to the greenhouse (to one water proof switched un-fused socket)
It may seem a lot running off the one 15A MCB in the house, but it has never tripped as there is not a lot of power used outside (Two pond pumps, a few lights, and the occasional use of hedge trimmers, strimmers, power tools and Christmas lights!)
Does this all look OK or not?
Everything is electrically protected as far as I can see (There are no cables rated under the rating of its supplying RCD or MCB)
The things I am concerned about are...
It is all earthed from the house - should I install an earth rod at the workshop, garage or both? (I have installed an earth rod for the generator witch is located next to the workshop - could I use this one rod for two earthing points?
The overhead cable is just bog standard T&E - I expect this should be either in a pipe of some sort, or armoured?
The cable that runs up to the garage is also bog standard T&E - it is protected by the water pipe it is in, but should it be armoured really?
Should I replace the old fuse box in the garage with yet another RCD/MCB box?
People say you should not have RCD's connected to RCD's - why? - Surely is it just more protection?
Thanks for you comments!
Sparks
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Sounds right>(via a sealed (metal loops of wire with a lead

This is the suppliers seal and should not be broken>the electricity board to come out and

block ( connection device for 25 mm tails ) for your outbuilding supply rcd.

You have a MK split consumer unit with your ring circuits being RCD protected>
Off the 80A RCD are the following MCB's (nearest to furthest)

They should be on there own circuits, 45A mcbs

Sounds right.>My first question is, is this correct - I am concerned that the wires that

If it is an MK split board it should be pre wired and the protection should be ok
For your outbuildings, I would do it this way, from Henley block 25mm tails to 30ma RCD and 2.5mm to your first building to a consumer unit. If you use a catenary wire, ( overhead ) it must be earthed at the house end from your main earthing point. and your 2.5 mm supported every 250mm ( cable ties ) . At the consumer unit provide an earth using an earth electrode, get this tested, the earth electrode resistance must be below 200 ohms. Then design your power circuits, ring circuits protected by 32A mcbs, radials by 20A mcbs and lighting by 5A mcbs The 25m garage run if underground should be in SWA using glands to metal boxes then for extra safety connect it to a FCU. Hope this has been of help, if you can not understand this e mail me as i have a great diagram which is very clear and i will send it to you
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