Second home sold to developer with option - CGT deductable?

I have read too much on CGT! Just sold a second home (couldn't sell it 15 years ago when we moved out or in the interim, despite trying many times) with a tennant in. The developer that purchased it used "An option" to make the purchase work for him. Our solicitor gave an option on the option, but never mentioned CGT liability. Now discovered we have 60 days to declare! Roughly speaking (need to find the paperwork), house purchased for £92k in 2006. Sold now for £72k (that's what we received) under the option agreement, recognising the work required to bring the house up to the street value of £105k. The Sale price is recorded as £105k, the difference being passed to the developer as a fee covering their costs. In terms of the "money we received" it's a £20k loss, but in terms of CGT? Is CGT due on the (£105k - £92k) £13k? Or can the "option fee" be deducted in the CGT calculation meaning no capital gain? Many thanks.

Hi PC,
HMRC are unable to comment on the Capital Gains liability here as we cannot see the option agreement or purchase agreement. However, guidance can be found on options and taxation at the following:
CG12300 - Options: definition
and
CG12311 - Options: taxation: option to enter into non-sale transaction and options to both buy and sell
and
CG12312 - Options: grant of an option
and
CG12313 - Options: exercise of an option: grantor of the option.
If you would like to discuss your own personal situation in more detail then it would be best to contact us direct
Self Assessment: general enquiries.
In the meantime, it would be advisable to report the full amount for Capital Gains within the 60 days in the first instance as this can then be amended as necessary.
Thank you.