Tried a few more gins recently. Verdicts:
Hendricks: I'm not keen. I can see where they're going with the cucumber flavour and I can see why some people love it, but it's not for me.
Gin Mare: everything I've read has said not to garnish this with lime (or any other citrus), as supposedly this will overpower it. But I had this in a bar and before I could stop her the bartender had already added a lime wedge, so perhaps I haven't really tried this properly. Regardless, I could still detect a hint of Mediterranean herbs, which were nice but didn't blow me away. It's pleasant but didn't particularly justify choosing this over other gins in the same price bracket. I might revise my opinion if I can try it again without the lime.
The Botanist: it's nice. Very pleasant. That said, if all I want is a nice gin I can get a bottle of Beefeater which was on offer for £18/l in Waitrose last I looked. There are some hints of unusual botanical flavours under the surface, but nothing exciting enough to justify splashing out. I'd be very happy to drink this again but can't see myself buying a bottle; again there are other gins I like more for the money.
Still to try:
Opihr: This sounds interesting, is available all over the place and is also pretty cheap (generally under £20 a bottle) so if it's good I'm onto a winner.
T.O.A.D. Oxford Dry Gin: made locally, with attention to sustainability, and I've read very good things about it, so I feel I ought to give it a go. It's pricy, though.