OK,
First thing I say to everyone is go and hold some rifles. Find a good RFD, speak on the phone, check they have good stock in new and second hand then take a visit. Hold them, feel them and that goes a long way to knowing what you like.
Then do the pro's and con's
FX Normally you can make changes - massive array of accessories and possibilities
BSA / Air Arms / Daystate - awesome kit, but not as many options as the above - but many prefer the styling and feel.
New Element Helix scopes are coming so thats an easy answer.
Shot count is important - example Sub 12 - FX Impact .22 - 650 shots per fill - thats the max on the market, cylinder guns are less and need filling more often but use less air to fill.
If £1500 is your budget then do spend £1000 at least on a rifle - it will get a nice piece of kit.
BUT - disregard all I say if you walk into a store and love something - back to my first point......
Not easy to make the choice but very enjoyable.....
G