"I was loooking for a weatherproof fitting with an electronic ballast and only after much searching I decided upon this Thorn 58W fitting as it wasn't easy to find on the Screwfix website.
The unit isn't the cheapest but is fitted with Tridonic ultra-high efficiency HF ballast which has a input power less than the nominal lamp rating. Power factor is 0.97, only 0.03% from the ideal. On paper better than the Lap units.
Also, on opening, it was a pleasant surprise to find that the fitting (as well as the ballast) was made in Germany,
Very easy to fit, screws are started and then the fitting is mounted, clipped on the screws which are then tightened. Easy to wire up with push-in terminal block with looping facility all minimises overhead working.
Short warm up time on the tubes after which the light is excellent.
You do need a 20mm conduit adaptor though.
Too early to tell about reliability, but should be OK if the Tridonic website claims are to be believed.