To cut a long story short, the first new hose was incredibly stiff and hard to work with, and not the right shape at all. After a few attempts, dropping and raising the fuel tank each time, I started doubting I had the right filler neck tube(!) Luckily someone measured their known to fit tube off their Series 2 and it was the same as mine so I started to think about the hose more. I still didn't know I had an unsuitable part but as I'd by now cut it too short I decided to start again and order another one.
The second hose I bought was specifically described as being for a Series 2A, rather than a generic 'FILLER HOSE 88"'. When it arrived I could tell it was a better shape (it has to bend down first at the point where it goes from wide to narrow, and then to the right and down at the right angle to mate the tank), and it was also cleaner inside and much easier to bend by hand as well.
The filler neck tube is now sealed flush with the tub and the hose fits neatly.
