At James Hooker's site are written, that the Thron 2D lamps and their bayonet adapters were kidnapped from the shelves and gain tremendous popularity in UK homes, not different than that of todays iPhones and iPads.
Why!?!?!?!?
I ask this, because this stands in direct contrast to Israel, where they were a brutal commercial failure, and had an extensive use only in the commercial sector, as an alternative to linear fluorescent lamps and PLs. Also, the adapters of the Thorn 2D weren't marketed in Israel at all.
Indeed, the only 2D fixture, that I ever seen in a home in Israel, was the first home of my father, at David Bar-Rav Hai 58 st, after he divorce from my mother.
Compact fluorescent lamps began to gain popularity at homes in Israel only at the begining of the 2000', with the appearance of Eurolux CFLs.
Actually, I began to buy CFL, MANY YEARS BEFORE the CFL were actally a commercial success at homes in Israel, following Eurolux CFL began to be marketed.

CFLs before 2000 costed in the order of 70-100 NIS, would you buy it ?

Orion adapter with 18W PL costed about 80 NIS

Only those who were able to afford it, could benefit from it (and it did save money becaue of the energy saving, and the old CFLs like Germany made Osram Dulux EL lasted a whole lot longer than any today's CFL

The 2D lamps were in limited use through the 80's and early 90's. limited allmost completely to 4 bulkheads - Coughtrie CPS, Thorn Emi Club, Gaash meltlight knockoff of the CPS, and Gaash square meltlight. The lamp itself was unpopular and perhaps to expensive

Thats in contrast with what happens today, when floodlights with irreplacable CFLs are all around and nobody thinks of it when buying

In the whole region here today there are few places where you can get a 2D, and many 2D fixtures are staying with EOL lamps which were not replaced since the early 90's, and others are replaced in favor of PL (in the past) / CFL (now). Which is bad cause the 2D are quite good lamps

Ash: The Thorn 2D lamps, were originally designed as a direct retrofit for incandescent lamps via a magnetic or an electronic adapter with an E27 base, for household use, similar to our Eltam Orion PL adapter.
Following tremendous popularity of the lamp in UK homes, Thorn decided to apply these lamps with a different base, suitable for fixtures that designed for it, that have the ballast outside the lamp (Like what we had and still have here in commercial places).

Dor, I wouldnt say that the Thorn 2D was a huge sucess in the domestic application. I for one didnt know THAT many houses that had 2D adapters fitted.
The 2D however in commercial applications are a HUGE sucess. I still fit MANY 2D fittings per year. I always try and fit the switch start version.
The GE lamps are the best on the market. All 2D lamps are able to run on MAGNETIC gear!

Thats what Dor asked to begin with. Why abroad (and specially in UK, the origin of 2D) they were so popular, while here allmpst never to be seen

I wonder too because overall it is a good lamp and there were some great fixtures for it, especially the Coughtrie

Yes i can't really tell you, They were not huge in france either. A rare sight there.

2D lamps never took off here in the states I seen a few here and there but circlines are more popular here.

Circular fluorescent lamps are also more popular in Israel than 2D at homes.
In my mother home, we have two circlines: One 40W in my brother room, and one 22W in the kitchen.
In the hostel I live in, they have also fixtures for circular lamps.
Circular lamps in Israel at home, were popular usually at kitchens. I have seen in Israel fixture for three 22W-32W-40W lamps.
However, hardware stores and lighting storages, sells many T5 circulars, which are piece of junk. The regular circualr are much more reliable, with their magnetic ballasts.
Circulars with triphosphors are available.

I never liked them much, due to consistent bad experience - they would randomly lose vacuum after little use, in different fixtures i had, for no apparent reason. I dont know why

2D adapters were perhaps only probably in UK because they were sold under the Mazda brand name, and until the mid 90s Mazda lamps were the by far the market leader in British retail sales.  In other countries though, Thorn was practically non-existant in the retail sector.  In particular Philips (including its French-Mazda brand) and to a smaller extent Osram and Sylvania dominated the European market, and their stick-type CFLs almost completely excluded the 2D concept.