See if you can try to have a look around with the engine actually running, if it is a 'blow' it might be more obvious, and if it is a leak to somewhere hot, it may be evaporating off before you get there.
The fuel filter is a problem; you probably don't actually need to prime with a vacuum pump, but it will likely be a bit of a pain. Just more of a pain without the vacuum pump. What with the problem of securing it, that sounds like a job for someone else! As it may or may not be anything to do with the filter, you probably have to try to eliminate other things first.
I haven't really had identifiable troubles with supermarket fuel - plenty on here will tell you that they have, but, apart from low mpg on the Asda stuff, I can't say that I'm one of them, and, with a busy supermarket, I feel you are less likely to get water (/any rubbish from the bottom of their tank) in the fuel than with an isolated country station - but I'd still want to try Shell/BP/Esso for a short period, to see if that makes a difference.
- ukmartian likes this