So I couldn't wait until tomorrow and had a go this evening.
Removed the hose from the bulkhead and guess what - the previous owner had beaten me to it, no foam. Obviously I needed to try the other end and having removed the jubilee clip and pulled the pipe off I found the long foam bung. Had to remove the lot. After much effort managed to replace the bulkhead end (the other end with the clip was easier) then off for, dare I say, a hoon :driving:
Windows down and on my favourite stretch of straight road in second gear at 3,000 rpm I planted my right foot - ear splitting roar followed, at 6,000 rpm loaded 3rd and pushed hard - sweet mother of god, the howl of the straight six was sublime :evil: