Disagree Hips. My club have runners of that speed. And with this group, the Club will make sure that there is a male runner with them at all times. The faster runners will take turns in being the "guardian" on the run on a run-by-run basis. This means that the last one in the pack is NEVER alone. I believe this is standard practise at all Clubs (that's what I have been told anyway). No reason why a 12min miler won't improve the same as a 6min miler or 8min miler. The speed and hill sessions are there for the taking.
Don't get me wrong, Hips, I know it's hard and I have done both speed and hill work and they are very difficult but only because I haven't done this type of trianing before not because the Club aren't considerate and accommodating.
It's very easy to not give the sessions a go because you know they are hard and resort to running instead and as a slower runner (me included) you don't want to think you will be at the back... Only natural but by throwing yourself into it, you'll find that the majority of runners are very supportive and don't care if you are at the back or not. It's all in the mind of the beholder (so to speak). I decided to just go for it and am so pleasantly surprised at the outcome.
The worst scenario is that you/one gives it a go and starts at a Club, gives it a couple of weeks and decides it's not for you. Nothing wrong with that. All I'm saying is do give it a go as you may be pleasantly surprised, like I was.