could be it's stuck in your mind now and your thinking too much about it. You could make a conscious effort to focus on your cadance rather than what gear your in, not much flat round Sheffield so I think your over geared a bit (too much Jan Ullrich not enough Lance), personally for me I'm on the small ring (12>25 on the back) up until 21mph or so, I have a natural high cadance but I reckon most people would get to 18>19mph without being on the big ring, as I was one told, you should only be on the big ring if your thinking of doing something ie a breakaway in a race etc. I'm starting to be on the big ring more now as my form is improving with the summer months so when I put the hammer down it's 25>28mph normally with bursts between lampposts/chasing tractors - the JCB 40mph variety!
Depends on your condition, are you racing regular or just out riding for health/fitness. I've never tried compacts but its a personal thing, if you try them and like them, it could be in the mind more than anything, would be some overlap in the ratios.