Early remortgage or money release

Dikey

We purchased our house in Jan 17 with a Barclays sboard (100%)mortgage on a three year deal, the house was initially valued at 177000 but we got for 138000 due to work requiring done. I have fully refurbished to a good standard in everyroom and I am current negotiating purchasing a sizeable plot joined to our house, I calculate the value to be around £200000 now. Question is what is the feasibility of releasing money from the now heightened LTV or getting remortgage early with another lender in order to release funds for the purpose of a sizeable extension on the newly purchased land which would take the value likely to £300000 with a building cost in the region of £60000. Facts only please