UK Tax Questions? Ask a UK Tax Advisor for answers ASAP
So long as the total plot of land that you own including that on which your house itself sits is no more than half a hectare in size (about 1.23 acres), you don't fence off the individual plots before you sell them and that the only expenditure you incur is on the cost of getting planning permission or the removal of restrictive covenants then HMRC will not seek to tax any gain and main residence relief will apply.
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I hope this helps but let em knmow if you have any further questions.