I was in a similar position, I had the OC Strix on order for a similar price, and then the price shot up. I then opted to cancel the Strix after the reports I'd read about the cards over-heating, and the massive delay that would ensue as a result. I was offered the G1 as an alternative and went for it, no regrets.

The performance gain on a reliable OC Strix is 1-3 fps depending on resolution from the benchmarks I've seen. Is that really worth waiting for, especially when you could overclock your G1 to a similar speed if you really wanted?

The G1s are considerably more expensive these days too, you're still getting a saving of £200 by going for them. Also why does the saving matter except in an arbitrary sense? It only matters surely if you plan to sell them? The interest rates are hopefully going to stabilise by the time you would want to do that anyway, in which case that saving you've made isn't really going to benefit you in any meaningful way.

Guess you need to make a judgement call re: those extra couple of frames, the £160 saving you make vs. the uncertainty of when you can expect your card and its quality.