Yes, you don't want a "spring gun / springer" [*], and skip any site with "BB" in the name unless you know exactly what you want and why. The bulk of what they sell is disposable tat, and in any case that's a realistic imitation firearm so they should be asking you to provide them with a defence in the form of a site membership / UKARA number (but being a "BB" site, they might not).
Airsoft isn't a particularly cheap hobby, you're looking at £30+ per day after buying BBs, and about £100 for the cheapest gun that you'd want to use [*].
These are the sort of brands and models that you'll want to be looking at, although other retailers are available. I've linked to the two-tones since that's what you'll be buying if you haven't played yet. You'll note that a lot of them are out of stock - this is the reality at the moment, we've hit a perfect storm of Chinese Virus, Brexit and loads of people taking up the hobby this summer.
https://www.patrolbase.co.uk/airsoft-two-tone-assault-rifles
All of these are select-fire electric guns meaning they'll shoot either semi or fully auto using a battery. Some of them come with a basic battery and charger, some don't (and curiously it's the cheaper ones that come with batteries), but you'll also want to budget for some lithium based batteries and a decent charger which is going to run you another £50 or so. Then add in (at least) eye protection and decent boots with ankle protection and you're knocking on £200 to get started with your own gear.
But the usual advice remains: play first, then buy. Most sites do a rental package which will supply you with eye/face protection, an electric carbine and a supply of BBs, generally for about £20 extra, so £40 - £50 total for the day. That sounds expensive but includes about £10 worth of BBs that you'd have to pay for anyway, so you're only really paying about £10 extra for the gun / eye protection rental. That's less than you'll lose on buying and selling anything if you find out that don't actually enjoy the hobby.
If you do love it (and bear in mind you'll get a huge adrenaline buzz the first couple of times you play) then you can go ahead and buy a two tone gun, or play at least twice more at that site over a period of at least 8 weeks, and that will get you site membership and (generally) a "UKARA" number which will let any retailer sell you anything that you fancy.
[*]One exception is spring shotguns, especially indoors / very close quarters, which can be fun and close to effective, but again, rent first and find out.
