I finally got around to replacing the rubber seal on the fuel cap. After removing the cap from the tank, I flipped it over and undid the two small screws holding the lock mechanism in place. If doing this for the first time take care to support the lock barrel, and note where the sliding plate fits into the latch, as it can take a few goes to reassemble it correctly.
After removing the latch assembly, swing the inner plate up on the hinge to reveal the E clip holding the cap seal in place.
Now here's the tip..........................
^ A couple of bits of 3x2 in the vice plus another spacer and clamp the cap in position using a valve spring compressor
^ Makes for easy access to get the E clip undone without having to wrestle with the spring underneath.
^ Once the clip is removed, release the compressor and it all just comes apart. Then undo the 3 screws in the centre of the cap sealer and flip the remains of the old seal off the lip
^ while it's in this state, I gave everything a good clean, in particular, the little round plate that sits inside the cap, as the hole in the centre of it is usually the cause of venting issues if it blocks up.
^ The reassembled cap centre with its new seal
^ Here's the top side of it where the spring sits.
Now it's just a matter of putting it back in the valve compressor to take the pressure of the spring and snapping the E clip back in place, then reassembling the rest of the cap. Easy as.