An afterthought on this...
Ivan, you say you "believe that £2 per gb over my allowence is over priced."
Yes, it's a bit pricey compared to most - but at £13.81 you're paying a pretty low base price to start with, and the thing to consider is, how often are you likely to exceed your 5GB allowance?
If uploading these films is basically a one-off rather than an ongoing project that's liable to result in, say, 8GB being used regularly, and the service provided by the ISP is fine in other respects, then if I was in that position, I'd stay where I was and live with a few pounds extra now and then.
For example, it wouldn't be fair to use my own package as a comparison, as (a) I'm on a 2Mb line not "up to 8 Mb" and (b) it's an old package that's no longer offered, but if I look at what Namesco's current "up to 8Mb" offering...
£14.95 with 1GB included
add a pre-paid extra 5GB for £2.50 = £17.45 for 6GB
or add a pre-paid extra 10GB for £5 = £19.95 for 11GB
or if my usage got more towards Kits's level of use...
add a pre-paid extra 25GB for £7.50 = £22.45 for 26GB
and so-on.
Personally, I'm happy with them and would stick with them if I upgraded my line - but if you are basically happy with your ISP, with that low £13.81 base price having 5GB included, if you're only a bit over, and end up paying £6 in excess charges, so £19.81 for 8GB, not massively over where the excess charge results in you paying, say, £29.81 for 13GB, you're actually no worse off, are you?
Namesco aren't the cheapest, of course, so if you genuinely need a *lot* more than your current allowance on a regular basis, obviously it's worth looking around to see what's on offer, but, as Captain Cretin says, beware of anything that looks too good to be true, because it probably is!
The bottom line is that bandwidth costs money, and you're not going to get a phenomenal amount for under £20 without also getting a really crap service. If Namesco folded up tomorrow, I'd be looking at ISPs like Zen, IDnet and the various Entanet resellers, and be prepared to pay a bit more for a decent service, not looking at Mickey Mouse ISP's 100GB for £15 or whatever - if you don't need 100GB, what's the point in risking it when it's likely to give you a permanent headache?
If Be sort out their current problems, their overall reputation is pretty good for the price, so they might be worth considering - but personally I won't use an ISP with an overseas call centre, so they they wouldn't be on my own list.