House vaulation for CGT purposes

I have a property (house) which I will be transferring to a child in the form of a gift. This is not my primary residence. When assessing the current market value for the property what sources/evidence do HMRC accept? For example, I bought the property a few years ago and can estimate current market value using the Nationwide Building Society (or similar) house price calculator which estimates current value based on purchase price/date and subsequent price variations since then. Would HMRC regard this as an accetable source for the purposes of CGT calculation?

Hi
Yes, the house price calculator you mention would be an acceptable source of market value information for Capital Gains tax calculation purposes.