What's the best brand/type of fuel for these engines?

I totally agree with you on the tesko fuel issue not being as good as branded fuel I recon they are using bio.and not getting the mix right because it doesent even smell like diesel anymore smells like washing up liquid and seem s to go throught my motor like a dose of salts .if you rember last year or more ago there werre issues in the east of England , i think with some fuels causing damage to engines because of teir biological make up was not correct .i use brand fues all the time and no way willi use apple green or tesco juice not even if its thirty cent a litre cheaper because if it gives you low milage or bad engine its going to be dearer in the long run so stick to shell.texaco .and BP .far better options in my opinion and better for our economys anyway..s

That is an interesting chart, but IMHO does not tell the whole story.
I must also be remembered that the fuel from cheaper sources may get you more MPG because it contains less additives (so is more pure, and has more fuel to burn), but this will not make a huge difference (or hardly any difference at all lol).
I have no idea if Asda stick with any one fuel provider (or fuel source) but it seems that Tesco are almost always esso in my local area.

One fuel I do not seem to do too well with is Texaco, although I have no idea whether this is because I mainly buy Texaco when I'm out in the country, and the fuel may have been stored for longer.

Either way, all fuel garages can only get fuel from their nearest dopot, and so most of the fuel in garages is the same stuff. The only differences being the amount of additives, and whether the fuel is 'winter' or summer' mix.