Hi,
You would need to decide if you are flipping properties as a trade, based on the facts of the case. If you are, then the profits would be subject to Income Tax, using the tax rates you mention.
If this was a one off, then capital gains rules could be applied. You can see guidance here:
CG15150P - Capital Gains manual: introduction and computation
Only improvements that enhance the value can be claimed as capital allowances.
Thank you.