As said you really need to decide what kind of shooting you like doing. Are you just shooting at the club, or can you shoot in your back garden?
For £350 you could get a really fun but tricky to shoot springer or gasram! Club members always like shooting another springer for fun.
Or put yur budget into one "all rounder" PCP, that you could use everywhere until you know what you really need. Best if you can find something that fits you, and not overly heavy or sophisticated.
Whatever the rifle try to ensure it has a known good trigger, as for a beginner thats if anything is more important than the rest.

There are plenty of good second hand rifles to be had, do buy one under used and not tampered with. Don't buy someone else's basket case. Stick to popular well respected manufacturers and models. Make a short list and see if you can try each for size. Look through a few scopes too.
We are spoilt for choice and eveyone has there own favourite. Without knowing more about you then its its hard to recommend. Most modern PCP's are pretty great already, the rest is personal taste.
Your first air rifle is just the first of many!