Different food....I betcha in London. Food can be a real trigger.
Think back to what was different there. Did you eat more fish there? Fish provides Omega-3's which heal nerves. Most Americans don't eat enough Omega-3's on a daily basis and have many problems as a result. Fewer tomatoes in London?

The nightshade family (tomatoes, potatoes, peppers including hot sauces etc, eggplant) especially can really cause problems! I have that. I think I mentioned those.

Picture your scalp as a thin tissue with nerves running all thru it.
Then WHAM you hit your head in the bicycle accident. What are the nerves to do, being crushed against the helmet straps and the bones in the head? The back of the neck can be really a source for many headache symptoms and pain. You could have a form of whiplash there. That is why the lidocaine worked.

Look at the difference between a football helmet and your bike helmet. They are very different.

At night you are lying down and putting pressure on your head. Even with a pillow. Then that part of the head heats up, temp wise and as it heats up then the nerves may wake up and start to fire. Also at night in your body, your circadian rhythm of cortisol production falls as 4 am approaches. This is the lowest time of the 24 hr day. So any inflammatory thing going on with you (and many PNers have worse pain at night), starts up.
Have you tried an ice treatment on the back of the neck and head before bedtime? Every day, say for a week. If this works, it would tell you something. If it doesn't, then you move on to another experiment.

One experiment many of us do is the AlkaSeltzer trial.
If you can use aspirin, try taking one dose (2 tablets in a pack), before bed. AlkaSeltzer original formula with aspirin, blocks both histamine receptors (the bicarb blast) and the aspirin will provide some anti-inflammatory action which is very very fast. The aspirin in Alka Seltzer is very quickly absorbed once your swallow it--it is in solution, and blasts into your blood stream and blocks burning, stabbing pain better than tablets of aspirin. It is somehow because of the effervescent delivery. It is easy and worth a try, if there is no contraindication for you about aspirin.
This works for some of us, and not others. I've found it very good for "attack" type pain. But some people here don't get the same effects. I use the WalMart version of AlkaSeltzer and it is very inexpensive! And I don't use it every day either.
If you are game, try it at bedtime, followed with some more water, to protect your stomach, each night for 7 days, and see if the attacks lessen or stop then. That will tell you about histamine effects and inflammation's roles.

Your medication, Tegretol, is good over the short haul, but carries substantial toxicity over time. Most people end up not using it anymore. It is the first line drug doctors use for trigeminal neuralgia or stabbing intermittent pain. So while it may work now, you might not last long on it over time. And it is very sedating too. This is why gabapentin is pushed more often, as it is less toxic over time.

But I think you can find a way to lessen your attacks with some attention paid to lifestyle, food, and some supplements. We'll get to those later.