imo , if you are going to spend that amount of money, which is a hugh amount, wait until a vintage set of autographs , with brian jones comes up at an auction and then bid. You will even have £/euros/dollars to spare as well!! And at least, imo,you willhave spent your money on a solid and nice purchase. there are a couple coming up at auction in a couple of weeks
Greig is reputable but getting second opinions is always a good idea, like you are here. But I'd get an online opinion from Roger Epperson (REAL). He's tops in classic rock. roger@rogerepperson.com. He only charges $15, and today I saw on FB that he's got a Cyber Monday special at $10 for online opinions. Well worth the money.
£1,450 for a band-signed Stones LP is surprisingly inexpensive, BTW, especially from a dealer.