i posted about holdalls not so long ago and have recently bought one (a one on weels) for the same reasons as yourself - luggage allowance. We got ours from argos and i was a bit worried at first because obviously you cant see them before you have bought it but, we are very pleased with it. It weighs next to nothing (2.4kg) but holds i think it is 103litres, so fits loads in and is made of really strong material so i'm not worried about it lasting the journey anymore. It was on sale as well so got it half price which is always a bonus. I dont care very much for the design of it but who cares at the end of the day!? and at least it will stand out on the luggage belt.
The reviews are not very good, but i have to say ours is not flimsy in any way, infact the material is quite 'thick' and very well stitched and is of good quality, anyway here is a link to it
http://www.argos.co.uk/static/Product/p ... uctReviews