I think that for me, the niggling concern I have is that in the time that I am waiting, my condition could worsen and prevent me from having a BMHR. I was told I needed either a THR, or a BMHR a couple of weeks ago my consultant suggested I have a think about it. I have thought about it, and given my age and the fact that I'm still very active (even though it can be quite painful) I'm opting for a BMHR. I'm seeing my GP next week, so I assume the clock starts ticking then on the 18 weeks. However, its likely to be about 22 weeks for me, as I have a major work commitment that will end in July. From then onwards, I'm not committed to anything else for several months.
To be honest my consultant didn't stress any urgency, and as I said, I've been living with a declining hip since about 1975, so I'm hoping a couple of months wont make too much difference.