Hi. My name is*****'m looking at your question now and will post my answer or ask for more information here in a short while.
If the profit is taxed on you as a sole trader, you would also be liable to Class 4 NIC unless you are over state pension age at the start of the tax year in which the profit is made. The Class 4 NIC charge would be £3,484.60 (£8,060 @ 0% + £34,940 @ 9 % + £17,000 @ 2%).
Given how long the development and sale would have taken from start to finish, HMRC may say that the profit is subject to Capital Gains Tax which would means the interest charges would be disallowed increasing the profit to £90,000. However, you would get the annual CGT exemption of £11,100 leaving you with net taxable gain of £78,900 on which the maximum CGT would be £22,092 (28%) if you are a 40% or 45% taxpayer. If you are a basic rate taxpayer, some of the gain would be taxable at 18%.
I hope this helps but let me know if you have any further questions.
You won't pay Income Tax/NIC and CGT.
You could disclose it as a capital gain but the planning permission implies a trading enterprise.