Ahoy and welcome, M'lurd.
As above, just find a local site and get in touch. You may have to hunt them down on Facebook, some sites can be poor at promoting themselves.
Pretty much every site will do a rental package to get you started, then you can decide whether you want to sink money into it. No problem with turning up alone, you'll be given a safety briefing, and airsofters are easy to talk to - ask someone about their toy gun and you've got a friend for life. You'll be rented some god-awful mesh mask, but if you have your own decent 2mm+ polycarb shooting glasses, and they don't fog up when you're running, they're probably going to be OK - plenty of folk wear wrap-around EN166-B rated glasses.
What you might find surprising is that you can buy 16J metal pellet air rifles that Joe Muggle couldn't tell apart from a bang-bang firearm using just some ID, but airsoft replicas require you to provide the seller with some evidence that you're a regular player. The UKARA system is one (but not the only) way - again, ask your site for details, but it basically means playing at least three times over a period of at least 8 weeks, they you're good to blow your pension fund.
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