I had the DBE water pump conversion on my JPS #188. It appears to have been well made and had no issues (see pic) in service. I ordered a spare belt and WP cartridge as spares. If I had kept the car, I probably would've ordered a couple more as spares. There have been a few companies offering WP conversions that have gone out of business leaving owners SOL in getting replacement cartridges.
I'm not knocking Burton Power but I ordered a water pump conversion that had fitting issues on my Elan. The front cover kept fouling the timing chain preventing the cover from fitting on the engine.
On the TCS Europa the main reason for fitting a cartridge/cassette type water pump is not to have to pull the engine in order to replace the water pump every time it starts leaking. To me that is well worth the money spent especially if starts leaking far from home.
No experience with the Davies Craig electric WP but it may be the way to go for owners in hot climates and continuous stop and go traffic.