SAYE/BAYE shares and CGT losses

[PensionerToBe]

I have some shares acquired via SAYE & BAYE company schemes which are now a shadow of their former value and I wanted to sell them to realise a loss to mitigate a gain

My question is around whether because they were acquired under a tax efficient wrapper this is possible or whether they are CGT exempt and therefore not a runner?

I've asked the Registrar and they've referred me to the company - who in turn have referred me back to Computershare

Any advice appreciated