OK. So, with the lack of recommendations, I tried using self-adhesive 3mm coachline tape (bought on Ebay), which works rather well on the straight and larger radius curved sections.
However, as suspected, the tighter curves (especially the semi circle at the front of the tank) simply do not work. If the tape is stretched to suit the curve, it does not adhere and comes away ; if the tape is not stretched it bunches up and comes away.
The tape seems to react with the paint after a couple of days and really sticks. So, I have now tried holding down the tape on the tight curves with some insulation tape to see if will allow the glue on the back of the coachline tape to adhere.
I suspect that the only way to get it to work is to cut the curve out of a solid panel, so that it sits flat on the tank.
Has anyone managed to overcome this problem?