This seems to be your issue, you want a fixed rate but don't want to commit to locking it away. You need to pick one or the other. If you want immediate access to your money then you need to accept not getting the best rate.
Considering what's going on in the US economy, it sounds like they're about to anchor on the brakes as the high interest is stifling their economy, so I don't see interest rates going back up over 5% as the UK will likely follow suit.
Unless you're needing your 40k imminently, I would look at locking it away at the best fixed rate that's available today.