Installing a dishwasher

worth a try.

That is likely to be the only bit that is mildly problematic: I can;t remember the rules here..but you may end up having to replace the u bend and a bit of pipe with something else.

Water supply is dead simple these days, use one of these self cutting taps and you don't even have to turn the water off.

The waste depends on what you have already. It sounds like you have one of these or similar

Both appliances go before the U bend - its purpose is to stop smells from the drain coming back up into the sink or appliance.

Probably easier to change the whole trap, they don't cost much. Unscrew the old trap (bucket underneath) and take it to an independant plumbing shop (not a superstore), tell them what you want to do and they will sell you the right bits.

Just to make absolutely sure I've got this in my head - when I say 'before' I mean it's between the sink and the u-bend, is this right?

Sounds good, will have a go.

Cheers guys.

You could discharge it into the sink, possibly as a temporary measure. I did that whilst rebuilding a kitchen, and it keeps the sink very clean, discharging hot dishwasher detergent into it every so often.

I like the multitasking! Hmm... have now started wondering about the direction of the pipes. Will the waste pipe from the dishwasher have to point down the way all the way? And I take it it's ok for the cold water input pipe to go uphill? (Can you tell I've not done this before ;-)

Read the instructions. Usually the hose has to be raised to a certain height or the machine will empty out as it tries to fill. Some dishwashers support pumping out up a 3m vertical pipe (useful in some basements if the drain is much higher).

My parents had one of the early Rolls-Colston countertop dishwashers which emptied into the sink. We'd stack all the dirty suacepans & stuff under the outlet pipe so they'd get soaked by the hot detergent-y water making them much easier to clean. Maybe it went someway to ameliorate the appalling inefficiency of those early machines!

B&Q have a sink trap with dishwasher and washing machine connectors attached. However compared to the screwfix ones it's astonomically priced at £19.99.