The weather was perfect and managed 6k for the first time!
Unfortunately I had increasing discomfort at the top of my right thigh, otherwise I reckon I could have gone on for even longer.
This afternoon went and got my gait analysed, apparently my ankles bend rather strangely when I run, plus my current trainers are very floppy/bendy, all of which are likely contributors to the thigh prob. Now the proud owner of some rather expensive new Asics. Probably could have got them cheaper online, but felt it best to support the local sports shop - cannot get gait analysis online(?)
The guy in the shop was really helpful - he is a distance runner himself. He said my running style was quite good and that my foot landed pretty much midfoot. I said I would like to eventually run the local half marathon, he said go for it and gave me loads of advice.
Altogether a good experience - would recommend.