Assuming the property is never your main home, any gain will be subject to CGT. The gain will be computed by taking the net of disposal costs sale proceeds and deducting the purchase price, the costs of purchase and any renovation costs. The first £11,100 of your respective shares of the gain will be tax free.
There are two rates of CGT, 18% and 28%. The rate or combination of rates that you will pay will be dependent on the level of your respective incomes in the tax year of disposal. A maximum of £32,000 of the net taxable gain for each of you can be taxed at 18%. That figure will reduce by every £1 of income you have over £11,000, thereby increasing the amount taxable at 28% by £1.
I hope this helps but let me know if you have any further questions.
Let me do some calculations.
Gain for each of you £20,000 ((£120,000 - £70,000 - £10,000) / 2)
Annual CGT exemption £11,100
Net taxable gain £8,900
CGT at 18% £1,602
Had you completed the renovations and sold the property much quicker which is what property developers aim to do, then you would pay income tax and NIC on the profit. That would be more than CGT unless you borrowed money to fund the purchase and renovations in which case the interest you paid would be deductible.