We are in a similar situation as miketually, we are the ones the bought the reposseessed house though and did the work. We are just coming up to remortgaging now, however our current lender has just given us a valuation of what we paid for it, plus a bit of inflation without seeing it. Other lenders are asking how much we think it is worth, however playing with the numbers it can make a massive difference to the equity bracket and interest rate that we fall into. But from my experience the mmortgage valuations will just say yes or no to what you think it is worth originally.
Zoopla is no real help as only 2 other houses are listed one is from years and years ago 20+ and for that price you wouldn’t get a shed now. The other is about 5 years but we think they paid well over the odds for it, then there is ours.
Funnily enough we have phoned reeds rains up, to come around and do a valuation as though we are selling it which is free.