Probably worth more like £150-200ish. Proper 12 ft-lbs classic 70s/early 80s springer. The shorter 55 got most of the attention, so the 60 and 70 are the less well-known "sleepers".
SILE were/are a stock maker in Italy who made stocks for a lot of guns.
Check out the online "Vintage Airgun Gallery", curated (posh word) by our very own Garvin, for loads of detail and pics.
Is the barrel slightly bent upwards? Or is that impression a function of camera angle, lighting, and/or the device on which I viewed your photo?
BSF triggers can wear to the point at which they become unsafe. Be careful with that.
Someone () on here claims to own a rare BSF65.