Well, I guess it's reassuring to hear others having the same problems....
DS never slept through either Luey but he was getting so much better at 5 - 5.5 months. Then all of a sudden, just before 6 months - constant waking. At that point we hadn't really started solids though, just giving him the ocasional taste of things. At around 6.5 months started having regular solids. I experimented giving him more and less and none to see if it made a difference. one 5-day stretch with no solids seemed to help for a bit, but then he went back to waking lots. Have just gradually increased the solids since then (on 2 small meals now, never dinner).
He also seems to need an extra feed during the night now.

Last night he rolled over and went to sleep on his tummy and slept 6 hours straight, the best he's managed in over a month!

I pulled the spare mattress into his room and have been sleeping in there for most of the past month
Also, found that leaving a dim light on seems to help (think it's becuase i have it on when I'm in there so maybe it's a signal to him that mummy's around)
Tried Brauer's stomach calm, which has helped him before, but no dice. Same for the brauer's teething relief.