Having had a similar unfortunate incident in a motorcycle vs Chelsea tractor dogfight hopefully my experience will be of use. I managed to smash my back up fairly badly and spent a few months flat out, dosed up to the eyeballs. The damage was fortunately quite light (as far as back injuries go) but didn't stop it being crucifyingly painful at the time.
When I went for for my initial class 2 I declared the incident, along with the fact that I still took the fairly heavy-duty stuff on occasions that required it. Letter from the GP and the CAA were all happy. A year or so later I went to Gatwick to get a Class 1 and it was barely even discussed; condition unchanged, medication unchanged. Now got a CPL, do a bit of instructing etc...
Interestingly every time I see a new AME I get an identical response of "that's not permitted" until they check out my record on the CAA database, shrug their shoulders, mumble a bit and sign it off. Whilst I genuinely feel the CAA want to be as helpful as possible with medical matters (colour vision specifically excluded) I am aware of numerous examples of double standards and sometimes wonder if there's a bit of "oh bugger, we shouldn't have let that slip through; oh well, just have to live with it now" going on.
If you've been off it for years I really don't think you'll have a problem at all. Medication prescribed by a doctor is taken in the best of faith.