What share price to use in CGT calc

I've purchased shares in the company i work for under sharesave schemes (2007 & 2009). Since the purchases and maturity there was been a rights issue in 2020 which diluted the price and increased my holding. It was also offered to buy 3 aditional shares for each 10 owned after the increase @32p per share. how do i calculate the buy price for these share to allow me to work out how many i can sell to remain with the current annual CGT allowance ? i bought one block (of 1211) at £4.16, and the next batch (of 722) at £3.87. after the rights issue, this became 5083 shares, plus an added 1525 shares (i bought at 32p each) - totalling 6608 shares. I think ive read that for mutliple purchases in the same company a single value can be used - is that correct - then if so. how do i calcalate that value based on the above ?

Hi,
Please refer to HS285 Share reorganisations, company takeovers and Capital Gains Tax (2024)
Thank you.