Another vote here for one of the stacking systems as a starter system!
18 months ago I was almost in exactly the same position as the OP. I'd decided I fancied building up a vinyl collection and started looking on ebay for turntables, stumbled across a few B&O stacking systems which directed me to Beoworld, where I was sucked in by the enthusiasm for all things B&O, and it's been down hill ever since! 😁
I ended up with a full Beosystem 5000 which I picked up for £325 and love, however as others have said it does limit compatibility with active speakers and the later remote controls, so I would recommend looking for a 5500. I have since replaced the Beomaster 5000 in my system with a 5500 for those very reasons (which I was given free very kindly by Peter!). The 5500 seems to be the most common of the vintage systems on Ebay so you will have more chance of finding a good one, and the prices for them are generally quite a bit lower than the 6500/7000 systems which as John says you will struggle to get with a turntable in your budget, even without speakers. I would recommend trying to find a full system going as one lot as you will probably get it cheaper that way than buying the components individually - if you manage to find one you should be able to get it for less than £400. Plus although as Peter says you can't use the latest active speakers, you can still use the active Beloab Pentas or Beloab 4500/5000 range which IMO are the best match for the stacking systems anyway.
As for the beocenter 9500 as much as I love the looks of that range (I have a 9000 in the bedroom) they tend to go for £400-500 on their own and the matching turntables don't turn up that often and when they do seem to attract a price premium. Similarly, as fantastic as the Beosystem 6000s and 8000s are (I did have a BM8000 in my bedroom before the 9000, but sold it because I didn't need the power), it might take a while to build up a full system as they aren't as common as the stacking systems, esp. with turntables, they take up loads of space, and they are more likely to need work doing on them. All just my opinion of course!
Having said all that, the great thing about buying vintage B&O is if you buy well you can easily change your mind and re-sell what you bought for the same as what you paid, or even make a small profit!