You should ring and ask about insurance if you put a 1.3 in it,i wont be that much as a 1.3 SR is only group 5 insurance anyway.
They usually insist on uprated brakes and suspension for engine upgrades though.
Cant hurt to ask,and it doesnt matter when you took your policy out,weather it be yesterday,a month ago or ten months ago,just ring up and ask,you may be pleasantly surprised!!
Tuning a 1 litre is a complete waste of money though,unless you buy parts that can be reused on a bigger engine when you do get one,like a cone air-filter or an exhaust.