Richy,
Sorry for the late reply, Thompsons, Ronseal etc are DIY products in my view, I use Resiblock, expensive yes but the results are worth it. Tech-clean also do a paving sealer which is supposed to be very good, I have not used it myself.
Here is another sealing product to look at,
www.swiss-seal.com again have not used it myself.
There is a guy on here , Driverwasher if not on here then on one of the other cleaning forums that uses a different sealer, I have spoken to him and he really rated it, sorry I can't remember what's called.