My tax liablity on cash gift from my mum

Some years back and with my mum's permission I applied for planning permisson to build a small house on her farm. Changes in circumstances (separation etc) meant I didn't go through with the build and was left with full planning permission and a small plot of land. Her intention was to give me the quarter acre. Some time later a friend of mine came into some money and said he wanted a plot to build on if I knew of any. I said I had one (I had spent nearly £5000 getting full planning including full set of plans) so agreed to buy all at £81,000. Several weeks later all is through and today my mum received a nice cheque for £78,915 (£81,000 minus search and legal fees). can anyone tell me what is her tax liability and what is mine given that she wants to give me the money received to help buy a new home?