There is no closed season for selling bikes here, except dec/jan might be a bit slow but prices do not drop.
Some bikes have good spares back up but quality varies immensley from good to rubbish.
One of the best spares services is for Matchless AJS machines via the owners club. I know they haveat least one member in Israel.
I think Norton Commando spares are fairly good as well.
I can't comment on Triumph; You will find spare parts shockingly expensive, and with frieght charges on top, ouch.
I think you should search ebay or the other link I gave and then talk to the sellers, I'm sure if you could give a date for collection they would help.
BUT, and a very big BUT, I should warn you that so many here have been badly scammed by overseas buyers they will be very very wary, maybe even refuse to sell.
Stay way from London it is an expensive dangerous sh!t hole, and most small businesses moved away long ago; probably the only bike sellers are for Japanese/chinese stuff.
I fear you are having a vision of a UK that has long gone.
For myself I am wary of Israeli guys and bikes because they fill you up with beer
Long story, but a funny memory