just my thoughts/opinion
i live in a town with a 100ft back garden
can i legally get an air rifle and shoot targets in my garden?
what cheap gun can you recommend for such a little place?
You have to buy your gun 'face to face' with the dealer now (in the case of shops, dealers have to be Registered Firearms Dealers), there's no mail order any more, though you could have it delivered to your local RFD. Private and 2nd hand sales are different, however.
As for where you can legally shoot... roughly speaking, anywhere you have the permission of the landowner. 50 feet from the centre of the nearest public highway and without causing alarm or distress to members of the public - or something like that. So back garden plinking will come under this last.
http://www.basc.org.uk/en/codes-of-practice/air-rifles.cfm have a look there, it will tell you all you need to know, better than I can remember offhand.
100 feet is plenty of room being ~30m this is the ideal zero range for most sub 12ftlb airguns, and is also a generally accepted limit taking into consideration, range and accuracy for hunting live quarry.
Better still if you can shoot from indoors out into the garden, might avoid the OMG!!11AGUN!!11!!11 type neighbours, who'll have the old bill knocking on your door in a flash. This is also a bonus if it's raining
As for where to start... there's lots of good brands to choose from Air Arms, BSA, Weihrauch... all of which have good starter type rifles to choose from, then there's the likes of Daystate, Theoben etc commanding more of the high end stuff generally speaking - though I don't imply that AA, BSA etc don't produce fine, expensive high end gear too.
At a glance, BSA probably have the best choice of less expensive rifles on offer for a beginner, followed by AA/Weihrauch, followed by Theoben etc. Those are what I have (some) experience with anyway. Webley used to be good, not so sure now though - they went bust, then were bought out, and now I don't think any of their kit is made in the UK anymore, though I could be wrong on this last.
If you're just starting out, I'd go with the self contained option of a spring gun, either .177 or .22 it makes little difference getting into calibre wars at this stage. You'll learn to shoot better with a recoiling gun too, over a dead PCP. It costs less to start with, and generally is easier to maintain.
Looking at NEW kit... say £200 - £400 for the rifle, maybe £50 - £200 for a scope (I recommend 3-12x44 as it's a very flexible magnification to use - the more you spend, be better quality of glass you'll get, so the sky's the limit really). Then you need mounts, some sort of case/bag for the rifle, and finally some ammo.
Most shops will usually offer some kind of 'deal' when you buy everything together. When I bought my first Webley, it was about £250 all in.
As far as targets go, I use a cardboard box stuffed with a couple of old telephone books as a backstop; take a bit of paper with some half inch circles drawn on it and away you go. Take that under advisement though, as I've been shooting for a while.
http://www.airgunbuyer.com/index.asp are good people to deal with, plus you can get an idea of a range of kit.
Be ware of the AirgunBBS forums linked earlier, it's a good site for information, but... and it's a bit BUT, it is populated by a lot of complete *****. Be wary of buying second hand off their sales section too; a lot of chancers. Cost me 150 quid some years back getting scammed by one of the members there. If you're going to look at second hand,
get it from a shop, not a private individual.
Go browsing, ask questions, post links here. I'm sure there'll be plenty of useful advice for you (and your wallet) to mull over