Thanks guys. Prices here really are scandalous for a lot of things. So much of what we pay is tax. I can order basic parts from the US and, with high shipping rates, it's still cheaper than buying here in old Blighty. That's why I'm thinking of emigrating. That and the weather!
I think there are so many differing opinions on things such as oil, chain wax, jetting etc that I end up stumped. We all want what's best for our engines and one man's wonder potion is another's poison. Perhaps it's a reflection of the commercialisation of everything - each product becomes 'the best' depending on who's doing the selling.
Walmart own ASDA here, but I haven't seen Rotella. Walmart probably own Triumph too, come to think of it...
Sky, I looked in Halfords. They said they don't stock the Mobil1 Racing 4T stuff. I've used Silkolene 10W 40 full-synth for my last change, so I have time to look around at the oils suggested here.