According to the calculator, it’d be about £280 assuming the purchase cost was £11k. I think that’s probably an upper-bound on the sale-price, though I can see bids of $20k on eBay.com for the same model.

I sold a domain via escrow.com a long time ago now (20 years or so) but the buyer paid fees, so I don’t know what they charge for that. You could try the calculator they have though (https://www.escrow.com/fee-calculator)

And thanks for the good wishes :)