Congrats!
I think that this is the way it will go over the short term. If I was to sell one of them, I'd try and go on to sell the other one quickly.
Domainers felt initially .uk being a threat to values of their domains. Then with .co.uk generally receiving the rights to .uk, it seemed like a big win (2 domains for the price of 1). In reality it's probably neither.
The value of .co.uk's may have been diluted a little but there's the opportunity to sell both, or keep one and sell one (or keep both).
There is an issue if the domains (brands) start competing, which if it's a high price domain there are probably big plans behind it and competition is inevitable - but not necessarily a big win/loss for domainers - just a different reality and weaker price of individuals to deal with.
I expect the price of the pair to get very close to the old price for the .co.uk (pre .uk)