For a UK legal radio with no licence the only choice is PMR, you cannot get 'better' range as the classification is limited on the aerials maximum output. But cheap ones may not even get to the maximum, so one radio may be better than another.
PMR also comes with the benefit of being compatible with other players if in use by a faction etc.
The ideal PMR for paintball is the Motorola XTNID, this is of a professional grade but operates on unlicenced PMR frequencies.
A benefit and disadvantage is this is programmed as professional radios are - you can switch between 16 channels and each one can be programmed to any of the PMR frequencies.
An 'ordinary' PMR lets you switch between the 8 channels and their subfrequencies at will.
If your team are on channel 1.01 and another team on your side are on 5.08 then you want to speak to both teams then with a standard PMR you need either two radios or have to keep reseelcting the channel and sub-frequency, whereas with a 'professional' one just preset 1 to 1.01 and 2 to 5.08. Click the selector back and forth.
XTNIDs are not cheap. In this case the price reflects the quality, but you can find them on the forums for as cheap as £40 secondhand
For more power you need a licenced radio. This comes at expense to get your radios, plus a licence to operate them. A compromise is to hire them. These come with the advantage/disadvantage that you cannot speak to other people who do not have the same licenced frequency, and there is the potential at some point in the UK that someone will have the same licenced frequency. (This should be slim as licences are issued with the intent of being seperate, but the same frequency will be issued to different groups, this does not matter when they are in different parts of the country, but if they paintball then they could meet - to guarantee exclusivity you have to pay big money)
http://en.wikipedia.org/wiki/PMR446
But also think outside of the box - if you need to communicate at a distance and a PMR is not up to it, get a mobile phone. Just make sure it is paintball safe, the provider covers the area, and you have credit or inclusive calls