Simon - your comments on the problem being car specific chime with comment from a lot of other people. Harvey is convinced that the answer is to make all the car systems, but particularely cooling, work as Rover intended. I think I agree but remain on the lookout for something bizarre.
So first up, "everything working as Rover intended". We've had one very good clue from a member down under - I think from memory in NZ - who did a top end overhaul and identified serious issues in his inlet manifold. It would appear that it is very possible to get the coolant passages in the inlet manifold very blocked indeed with gunk without necessarily ruining the ability of the engine to maintain temperature on the car gauge. That definitely sounds like something that would feed through into vapourisation. Also something that might actually vary according to how well Rover cast the manifold. So assuming you're confident in the cooling capacity of the rad (Fitted a three row core yet? That often seems to help in this respect as well as in guaranteeing adequate cooling under all circumstances) and performance of the rest of the system, use advanced search in the top panel and see if you can find the thread on inlet manifolds. If not come back and I'll identify.
Then, from your list of options, I'd go for No 2 first. GarethP6 has put up a thread on a mod he has done to his car which is extremely sensible indeed. He has taken a new petrol line from the bottom of the reserve tap, across the back of the engine bay and then up and out behind the steering idler into the inner wing area. He then runs the pipe down the inner wing on the road side and brings it back into the engine bay in the pocket behind the near side headlamps. From there it is an easy leap to the fuel pump and back into the normal pipework.
Next up I'd do No 1 and fit a recon kit to the mechanical pump, simply on principle. After that my personal choice would be to fit an electric pump in series with the mechanical pump with the electric pump located in the engine bay down behind the near side headlamp where it is nice and cool and where the afore mentioned rerouted fuel pipe enters (location again borrowed from GarethP6). I'd want to use one of these Huco pumps:
http://www.gowerlee.dircon.co.uk/HUCO.html from Gower & Lee in preference to a Facet. Not least because it looks period (although it's actually plastic) and because they give you a choice of specs which allow you to simply choose the correct one for the location - in this case I'd go for a 133010. Most people seem to go for a pump adjacent to the tank. I think this solution is superior as it doesn't leave your pump unseen in a particularely vulnerable location and allows you to use the original tank pipework and reserve tap. Changing the latter to suit a single pump at the rear is a pain and detracts from the car - you inevitably finish up ditching the reserve facility. I see no point removing the existing mechanical pump. It's extra work and the resulting pipework won't look right in a very visible area.
All that said, I haven't had to do any of this, as mine is in the select group that seems untroubled by the phenomonen. But I had expected to have to do it, so had worked out my solution in advance!
Chris