My fuel flap won't open no matter how many times I double click the open on key fob. Any ideas please?

Try gently pushing the flap while pressing the unlock button - it's not uncommon for the flap lock servo to get a little sticky.

Cheers I've tried the gentle tapping it's not having it. Luckily I have 3/4 of a tank

This might help:

Cheers pal I have ordered the part from auto doc and the removal tools from Amazon. Hopefully I can do it. Looks easy enough.

Is there not an emergency pull cord on the inside?

If there is I can't find it

It should be behind the right side panel in the boot. Unfortunately, as I've sold my Superb Estate Mk3 roughly 1 year ago, I can't check or don't remember where this is precisely. On Superb Estate Mk2, this was close to the rear right lights. A kind of red plastic pull tab...

Maybe a look at a 'How to' dealing with something in this area may help you locating it.