I'll try explain what's happened in a very short summary..
Me and my bf are first time buyers and we're going for a house that is priced at 128.5k.
From the beginning we stated that we would like to pay 125k (to avoid stamp duty) and pay the 3.5k difference, for fixtures and fittings.
It's right near the finalisation - we have been told we could have the keys by the 21st of July but we need to reapply for the mortgage so that it will cover the extra 3.5 as apparently the sellers have NEVER heard of this offer before?!.
We made this offer from the beginning and we were led to believe it was agreed that is what would happen on both sides!
It even states that we're paying 3.5k in fittings and fixtures in our mortgage confirmation package we received and now our solicitor is claiming their solicitor is disagreeing/never heard of it. 
I then rang the estate agents who advertised the house, who confirmed that they knew the offer was for 125 plus 3.5k fixtures and fittings and they have recorded conversations with our solicitor that also confirms she knew about it and said everything was going 'fine/well'. 
Soo my question is.. Should we refuse to get a new mortgage drafted and say to them, take it or leave it or should we pay the stamp duty?
( We can afford the stamp duty but it would make money tight for us, we are early 20s, first time buyers and don't have a lot of spare money! )
the sellers have moved out of their house already, so it's in their interest to sell it asap
ADVICE FROM EXPERIENCED BUYERS WOULD BE GREATLY APPRECIATED !