Why is it failing on a back plate? The shoes can be held in place with threaded 4BA rod, washers and nuts obviously with retaining springs in place, The back plate is only a shield, at worst an advisory.

No bud needed a plate welded to rear drivers side sill about 6 inch long

Post 8 you mentioned the back plates. Hope your doing both rear discs cos if you arnt then you'll have an imbalance and a fail on the rollers.

Mechanic hasnt no but it passed the imbslance testvin MOT on 12th just failed because hevsaid drivers brake disc looked bad and weak so he told me ro change that disc and weld hole in sill then when done needed a quick inspection to see they had been done and would get a ticket but i was wondering if they passed brake test on 12th but failed on looking weak, will he do another brake test or just inspection of condition, he said it would only be another £10

Humpty, don't be a numpty.

Stop listening to anything they're telling you - there are seagulls on my hedge who make more sense.

Get your car back, pay nothing, get a decent mechanic to look at it :)

I havnt worked in 3 months im needing car for new job on monday and am borrowing money from sister for tax, insurance and fuel so as brake disc had finally been done and welding almost done and i will get other brake done with first lot of pay can he fail car again on mot when he just said it needed a o/s disc changed and patch in o/s sill that is what is done

OK.
Without being nippy, do you really expect that a MOT failure done over a week ago will not require a retest? Firing on one new disc and hopefully pads and shoes is half a job and WILL fail on imbalance, whether you are employed or not. Sorry but do the job properly and don't faff around. Get the bus, lift or train till you can afford to do the job right and don't ask the MOT man to jeopardise his job, others safety or yours.

Having a ZT or 75 and trying to do the work on a shoestring is crazy in my mind, you've already been told of the rust on this car which you ignored now it's biting you in the posterior, sills and backplates so far...... what next when your starting a new job, I know for a fact you have asked for advice many time before on here and TBH you don't take it on board.

Hi,
You started a farm job last month.
Did it not work out?

No it didnt, and i was told its 10 days to retify faults, not many buses etc you can get in country to a job at 4am

I think you are "up that creek" why not approach your new boss and explain how keen you are to start work but tell him about your difficulty and see if he can offer any help.
You really do need a better repair shop than the one you have though.
Ken.