After a few issues with the standard mechanical pump including a leaking seal I decided to change the unit for an electric water pump. There was a lot of debate on the yahoo group about which was better but decided that I wanted to find out rather than just talk about it.

I had a look around at pumps that where easily available and seemed to be up to the task. The WC engineering unit has a unrestricted flow of 4gallons per minute and I took that as a base line.
MAW Solutions of Stamford is a distributor of the Davies Craig Electric Booster Pump that seemed to fit the bill.
The unit is automotive quality and seems able to handle the water oil and general muck of car engine bays. Relatively small to allow easy placement. Has an unrestricted flow of 13 litres a minute. Has a 2000 hour continuous running warranty and estimated motor life of 15000 hrs.

A couple of images of the standard mechanical pump.

The installation of the new pump was relatively simple.
First was the removal of the old pump. This was possibly the most awkward part of the procedure as it's a tight and mucky squeeze to get hands and tools down between engine and inlet plenum. It is vital and simple to remove the air box that gives the best access. Some people also remove the oil filter and give the car an oil change at the same time. This had been done recently anyway so didn't see it as required. I'm always up for a challenge :)
A valuable piece of kit is a flexible shaft screwdriver that can take 1/4" sockets to remove the jubilee clips.

Finally unit was out and it looked in reasonable condition, but I had previously replaced the rubber impellor the first year I had the car. The car can't be left with a whole where the pump is as it would just leak oil of course. I did try just putting the housing back after blocking the holes but found that I was getting low oil pressure on occasion. I think the housing needs to fill up with oil at before the oil pump starts working peoperly.
End decision was to fit back the shaft but to remove the locating key so that it would not spin. The water inlet and outlet are plugged up and impellor left out. This seems to work effectively. Also means I can go to a mechanical pump in future if there is any reason.

Fitting the electric unit, which was nice and compact, was accomplished using some new hose from Halfords so that I could have better choice of where it would go. Origional return to the front of the car was not touched. Feed to pump was I tried to keep the pump as low as possible in it's location to give the pump a good head of water. Also I made the decision it would be best to push cold water into the charge cooler rather than pull the hot out. This was done to reduce chance of any air pockets reducing pump efficency. First location was attaching unit to side of plenum.

This was fine but vibration from the engine was an issue possibly plus it could be lower. I then moved the unit under the air box and bolted it to the plate that feeds the HT leads. This is out of the way visually, low enough to provide a good head of water, away from hot parts and any engine vibration.

The wiring for the motor was done by using the wiring used for the vaccum pump. I don't have this pump since I've had the car so it seemed an ideal position. I may look into using the Lotus recomended rlay and link into the ECU loom. I'm always a little reluctant to start splicing into anything going to the ECU.

Verdict
After a few test runs it seems to be working fine but haven't done enough to fully test it. Using freescan before and after the pump was fitted I did notice that the temprature reduces quicker after an extended run. I think the pump holds a high flow rate even when car is just ticking over. On initial and sustained boost I didn't see any appreciable difference. Temprature still climbs very quickly and got to similar tempratures before holding. Any difference could have been due to difference in the outside temprature. Also it did take a few runs and top ups before the system cleared all the little air pockets in the system.

Overall I'm happy with the installation and think it is one less possible point of failure in the future.