No need to restrict your options to UK suppliers... if all you want is a a bright visible beam that's capable of burning things you'll almost certainly get better bang for you buck buying from outside the UK. There is also no way of telling if that company sells lasers that are up to spec.
You won't have your laser confiscated if you buy it abroad, but in some cases you may be charged duty/tax, depending on how your chosen supplier declares it in the customs declaration. Often they will declare a low value, so there are no charges at all, but you should check wit the supplier of find out from others who have ordered to be sure.
As for IR filters, as magonegro says, the IR from a green laser is not dangerous as long as you don't do stupid things with the laser.
If you want a laser that is up to spec, go with one of the recommended suppliers, like CNI, Opto, Nova or Laserglow. You might get a laser that is up to spec with someone else, but you are more likely to with a recommended seller. The gamble is up to you.
I can't recommend any particular laser, since I only have lower power greens so far, but I'm waiting for a 400mw from CNI, and those are almost always well over spec judging from reviews on here.
Overspec power is not the only reason to go with a trusted company though. The lasers from a better company will have better compnents, and will be less likely to go wrong, and in general, they will have a much more stable power output... if you buy a 100mw, you want it to stay at or over 100mw for a while instead of peaking at 100mw for a second or two, and going back down to 80mw right?
That is also why it's better to buy a laser that is bigger than a pen. Since they have bigger heatsinks the duty cycle will be better, and you will have longer diode life. Heat kills diodes!
If I were you, I'd take my time reading reviews on here, until you find something you are sure will meet you needs. If you rush it, you will probably end up with something that is not that good...