Hi Andy,
I'm not that far from your neck of the woods but nowadays I'm always on the Ham bands with a horizontal antenna setup so afraid I can't help you out not having a CB setup anymore.
I must admit that when I came back to the radio interest a few years back it was very quiet on the CB front which was why I went on to gain my Ham ticket and there's always something on air with those extra bands.
What sort of radio and antenna setup do you have?
If you have a SSB or sidebander rig there's been a lot of DX activity recently so always worth a listen and giving out a shout. If you have an AM/FM Euro & UK rig it's worth shouting out on the Euro frequencies too. (Propagation works for all modes.) UK FM can be very quiet depending on the location and like I said I found little activity in our area. (Might have changed since then?)
Worth a shout on the typical calling channels such as 19 every now and then in case anyone's monitoring.
(Make it more than one or two calls though on a regular basis to stand a better chance of success.)
The only other suggestion I can make is to listen out for your own transmissions with an online or web receiver. There's a couple of Kiwi SDR's (software defined radio) around here and you can find them at the following map link :-
http://rx.linkfanel.net/
Zoom in on the map to find your location and receiver sites. (I think there's one in Bedford and Northampton.)
You're in the middle of some surrounding population centres, (Milton Keynes, Northampton, Wellingborough, Rushden, Bedford) so should stand a chance even with local contacts. Not forgetting passing traffic where there might be CB traffic on the A428, A509 and the M1.
Stick with it and I wish you the best of luck.
Otherwise you could succumb like a few of us old b*ggers did on here and gain that Foundation ticket. Less than £30 for the exam, bit of study and even a basic VHF/UHF radio will get you started.
All the best,
Victor