Thanks for your advice Melanie. I contacted my supervisor today and as has become standard practice they were very short with me and I get the feeling they think I'm a bit slow.
Eventually I found that the decrease was due to an increase in the amount of debt at the initial meeting and the £800 I am short.
I am now extremely nervous that this offer will fail as the supervisor painted a very negative picture and I am now convinced it's not even worth making the offer.
I have signed the forms so fingers crossed I get a yes but at the moment it's not looking great and I feel I have gone from it nearly all being over to another 2 years of payments.
Anxious times and all caused by previous stupidity I know
Thanks for all of your earlier comments