I have had my fingers burnt by a "no win no fee" company before thinking that they were the people off the television who promised 100% compensation, but when my claim went thrrough, the solicitor ended up taking a big chunk of my fee. I obviously wasn't happy, but this made me realise the difference between no win no fee, and 100% commission. I think really, you should only work with people who offer both 100% commission and who operate on a no win no fee basis.
the people you've mentioned in your question i think are the people from the television who do really offer no win no fee and 100% compensation. I've had a look at their website (http://www.national-accident.co.uk) and seen that they have a good section on no win no fee which actually explains how this works:
http://www.national-accident.co.uk/no-win-no-fee.html
This explains who pays for the claim if you don't, and also can help you understand if you're even eligable for a no win no fee claim.
hope that helps