I have a 20M race at the beginning of March, I'm not sure I could manage it at MP and then get the rest of my training done well the week before and after. Not sure what Steve has planned for me in that race yet.
I think a fartlek a Dorney could be a bit of fun, like you say would get some strange and confused looks, but really its no different to using it as a MP effort!? Your right though, probably best to get it done outside of a race situation so I don't get sucked into running too hard for too long!!!
Steve....... I'm going to swap things about this week if ok, I don't feel up to 10x800's today, still not fully over my illness, and as its an important session would rather do it Thursday when hopefully feeling 100%. Feel ok today, just tired still, I think if anything just an easier run would be better.