I believe people have tried electric lifter pumps with limited success Chris, I believe Imperial do these still, but the "Roys" (or Tim B ) may have a better idea.

My bus number (if any): RTL 960, RM 1585 and several RTs

There are IIRC at least three types, but they are all interchangeable. You can get them recoditioned but it can be a bit hit and miss. The problem being the castings become porous and do not show up in the fuel injection w/shop as faulty because the only way it appears is when on the engine. Have word with Peter Salter FIE in Scunthorpe.He seems to be the nearest to you.

Does anyone know the part number for the lift pump, starts with DP3/..............

None of mine have a part number visible.

My bus number (if any): RMs 238, 471 and 2213, GS17

Looking back at previous threads and discussion about electric pumps by Mike Mann, the consensus is its easier to take the fuel pump out and clean out the lift pump/change/clean the filter. Looked at BEMS parts list can't find a separate number for the lift pump sorry.

My bus number (if any): RTL 960, RM 1585 and several RTs

I had discussions with Lionel moss a few years ago about electric lift pumps having had experience of them fitted to RMs abroad. The RM needs about 4psi at the lift pump, electric pumps give about 40 psi. Herein lies the problem; this excess pressure has to go back somewhere, and that is through the return pipe and injector spill-off pipes. Lionel reckons this excess pressure can cause internal injector problems as well as other problems in the return pipes as the system is not designed to cope with that high a pressure on the return side.

I've come across buses abroad with 2 electric lift pumps fitted, simply because the people there were too lazy to get the proper pump overhauled or hadn't changed the filters!

It should be easy enough to get your lift pump overhauled, and aren't the in-line lifters a steel pressing rather than a casting? We have one on our AEC generator set outside. :)

My bus number (if any): RML2532