Lenders attitude towards interest only lending has changed significantly in the last 2-3 months and the best answer I can give is to go and see a mortgage broker who can tell you which lenders will allow what and to what levels. Some now will allow a maximum of 50% of the LTV on interest only, most do still allow up to 75% and you are inside of this.

Go and speak to a mortgage broekr and he can tell you what you can do and who with. I will say that an expecred maturity of £85k lump sum will likely be sufficient for most lenders with the new criteria but you will need to check with the specific lender that you decide to go with. The lender will of course wnat to ensure that the mortgage is fully affordable for you to take on too