Hello 

Was always wondering why in the UK we have more of the 2D compact fluoresant fixtures than the circline types?

I know that the 2D fluoresant lamp was invented by Thorn in their factory in Enfield and since then it has been popular in the UK! Maybe the popularity of the 2D meant less fixtures for circline T9 tubes because in the USA we see countless fixtures using circline fluoresant tubes

Out and about with me in the UK, I see a lot more 2D lamp fixtures and I'd be lucky to see a circline fixture

2D invented by Thorn in the UK, the circular lamp invented by GE of USA under the trademark "Circline".

All comes down to that 

But the Circline by GE has been invented long ago before the 2D in the UK

Looks like the UK had the majority of using linear fluoreesant battens and probably few circline fixtures before the 2D came along 

I can say about here - Israel

In the 80s there were both PL and 2D trying to get in. In the early 90s they both were being installed, but by the mid 90s the PL clearly won and 2D became the little used, limited avaiability lamp, used by those who are "stuck" with 2D luminaires

The circline was moderately popular up to early 2000s, held in this position by the many low end decorative luminaires made at the time (out of nothing more than some very basic body, choke, and the circline+starter combined socket)

But in the end it fell out of favor. I think because the circlines present on the market here were of dubious quality (unlike the mostly good linears), and maybe by the 00's the old circline luminaires finally started failing too (crumbly Plastic parts after years of UV), so peeps were convinced that circlines are up to no good

The "2D" was just an evolution from the circlines, to allow standard interior lanterns to be equipped with more efficient light sources during the energy crisis in the 70's. Before that just the incandescents were used there, so no need for circlines...