how much research have you done into what is out there in terms of your flavour of paintball (woods or sup'air) or other markers available at around the same price (or less) than the A5 and X7?
'tis a bit of a minefield at first, and the last thing you want to do is buy one marker and decide in a couple of months you made the wrong decision.
for example:
where will you play? will the site run on air or CO2, or can they offer both? if they offer just CO2 then a marker like an A5 or X7 is perfect, or consider looking at the SP1, which will be faster and more efficient, and for £100 new is top value.
if only air is on offer then i'd definitely suggest looking at something more efficient than the A5/X7 as they have a tendency to guzzle gas.
will you just play in the woods, on the sup'air filed, or both? an A5/X7 would be a tad cumbersome for popping out behind bunkers on the sup'air field, but will be a nice robust marker for the woods.
as a first marker for the woods, i'd suggest the A5 over the X7, as it is cheaper, and does exactly the same job - just without the miltary rifle styling. for £100 tho' i'd definitely suggest looking at the SP1 before you commit to either the A5/X7.