Got it out yesterday after using the angle grinder and a dremel with the small 38mm discs.
Both side towbar mounting brackets need to be removed.
And as they may have been on since new, I had to cut the nuts off the thru chassis bolts.
Nice design, atleast on the right hand side, not too much space between the bolt and tank, got some minor heat damage on the tank now. Cut a little, grab some roadsalt etc grime ice and cool the bolt down, cut a little etc.
Had the nuts cut off and tried turning the bolts, no luck, nada, zip...
Spent atleast one 6Ah battery on my TW700 hammering them back and forth before they gave up and loosened enough so I could hammer them out.
Plenty of "loose" corrosion in between the tank and chassis etc, but it did come out.
Fiddled the new fuel pipes in and hopefully I got the two correct way around that go on the rear of the filter housing.
Getting the tank back just needed some rough handling for the filler hose to be pulled down from the trunk floor for it to have room to pivot in.
At this point I felt it was too crowded in my "garage"tent due to too many f**ks flying around, so I quit and went in to eat some reindeer and have a shower.