In this case vendor had an arrangement of service charge at 6% per annum.
The service charge appears to be interest and perhaps should be taxed as such.
How the transaction would have been treatment if eg the term were 8 or less than 8 years?
No difference because you appear to have lent the money to the purchaser rather than agree to an installment arrangement for payment of the consideration. 8 years is the maximum term over which CG tax can be paid where there in installment arrangement. The installment arrangement can be any length.
Secondly how one can proof that capital expenditure has incurred on property??. Individual Spend 86k towards capital expenditure but there is no invoice to proof all payments to builders were made by cash.
When the commercial property were sold in 2010-11 the market for property were really down. During that period getting a high consideration for property suggest refurbishment was done which lead to higher market value .
You need to demonstrate expenditure was incurred for the purpose of enhancimg the value of the asset, was not revenue expenditure, and was reflected in the state of the asset at the time of the disposal. If you have no evidence of a cost, you will have difficulty claiming a deduction. Nobody spends £86k without at least a written agreement of the work to be done and the amount to be paid.