Why mess around with tape when you can do a simple 2 layer paint job? I believe it's a fiver for a can of spray paint from Halford's- get a can of OD or dark green and a can of dark brown/black, give the weapon a base layer of green and add some diagonal stripes of black or brown. I understand this is permanent and removal might result in damage, but if it does you've bought a very poorly made rifle.
Assuming we're starting off with a RIF, another way would be to get some dark coloured elastic bands or silicone wrist bands (job lot of 10 for £4.99) wrap them around various parts of the rifle and add site specific foliage which can come off at the end of the day. I think this way may be better in cases, since different sites across the UK will have different seasonal colours within the local flora.
For example, you could be at a site populated with beech trees one week and need to camo up with the silvery twigs, but come the next and you could be at a site covered with fir trees and have the option to use them, instead of having 1 tone of camo tape or burlap (which may work for your 'home' site but might not for skirmish sites further afield).