Loft Conversion

I have seen there is alot of good advice on this site and was hoping to get some on the loft conversion I am thinking of starting.
I have just fitted a very nice set of wooden fold up ladders to gain access to my loft, I live in a terrace house so there is plenty of space to be converted there is a completley open space with no jiosts or beams to be moved to gain access my builder friend has tolm me that the main beams that hold up the roof have been reenforced at some piont with additional beams attached to them and placed in the party walls either side of the house at roof hight.
they have also attached supporting beams to stop the roof pulling away in the form of 4 x 2's in two 4.5m sections bolted together to form 9m lenths attached to the roof jiosts that the roof batons are attached to (dont know what these are called in the trade) and then cross nailed to the other jiosts spaning the entire roof lenth about 7 in total.
I have been told that I can replace these with steel banding and am going to do this soon, I was then going to put jiost hangers in the morter of the two party walls to suspend beams about 1 brick up from the existing open floor my question is this should I put the jiost hangers in the morter or use the jiost hangers that bolt to the brick which is the better and stronger option.
I am awair of party wall agreements but my next door nabour one side is a builder and he has just converted his loft already with out building regs knowing (only found this out today)so he has already told me that I am ok to do the work and our other nabour has also given us permision I am not looking to fully convert the room into a living atrea but I would like to know that it is safe and strong enouth if wanted to move my computer up there and use as an additional space. I am also awair that building regs would never pase it off due to not have a full set of stairs with a fire door attached so not going to class it as habitabal (no carpet,no roof window,no drywall) just going to paint the brick work and clean out the dust, I have already removed the loft insulation and got some chip board to put down in the form of loft flooring boards.
Any help on this would be very appreiated I am also dislexic so sorry about the spelling and grammer.
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