- we were quoted from 1500 to 800 for 'building regulations fee' in order
to
be able to do this - what is reasonable ?

Assuming you mean 500, that sounds reasonable for someone drawing or
submitting the plans / building notice and doing some admin.

no I meant 1500 - we were told 1500, 1300 , 800 - by 3 different salesmen

also they were quite confident that we will have no problem getting it
approved without doors as long as we pay of course. I dread to think what
happens if we pay but end up getting it 'disapproved' ?