A bit of a long story here.....
Back in 1971 the Weeley pop festival was coming up and I and 3 friends were keen to go using our own transport
I'd managed to scrape up the £10 needed for the deposit and talked my dad into signing the hp agreement
My purchase, from a dealer, was a '55 Golden Flash outfit LJN 354, fitted with leading link (Douglas I now know) forks, 16" wheels, a cafe race type seat, a Steib frame and a homemade sidecar body fitted with a high back car seat!
We pulled the seat out so 2 people could get in the body and 2 on the bike itself
Perhaps surprisingly (apart from a reluctance to start) the bike made it there and back without any real issues....the only problem being a tendency for the bike to slowly lean in toward the sidecar....solved by stopping every 20 miles or so and pulling it back upright!
That was 50 odd years ago and by coincidence recently saw a post about the event on facebook (it was the largest ever one in the UK), looked at some of the pics....and there the bike was!!
I can't say I greatly enjoyed sidecar riding (except when it snowed....I did take it to the Dragon once) but kept the bike for several years after converting back to a solo....fitting it with pre unit Bonneville forks and front wheel
I've been riding ever since and sold my last A10 a couple of years back so if its about (shows on DVLA) would be very interested to hear!
Interesting as my 55 Velocette has LJN as it's letters and the number is about 300 before mine. First registered in Essex I believe. No help to you I know.