Sorry to hear from all the baby show people that it wasn't worth it!
Urrgh I am at home again today - after not being able to walk terribly well on Friday thanks to my hips being rubbish and working from home as a result. Took it easy on all your advice for fear of SPD.
Attempted to go into work this morning - hips still hurting but could walk slowly (and was planning to take a taxi from waterloo to the city - I usually walk) but then a woman got on at twickenham and sat down next to me - cup of coffee, eating a chicken & mushroom slice, and shrouded in that sour smell you get if you leave your wet washing in the machine too long. Someone else standing up had really strong perfume on and my head started spinning and all of a sudden I just knew - I was going to be sick, or pass out, or both. I leant back and breathed through my mouth but only made it to clapham junction - when the doors opened I leapt to my feet, bolted off the train and was nearly sick on the platform 

Never in my life have I been so thankful for the indifference of London commuters - no one gave me a second glance so I sat in the fresh air for half an hour, called in sick and took the next train straight home again. Fell into bed and slept for 4 hours - after a full night's sleep last night!
I have had NO morning sickness all the way through and full of energy up to this point so I don't know what's wrong with me - guess it might be the "slump" someone else was talking about on the pg board but I'm worried that at 28 weeks, work will either think I'm taking the piss or ask me to take mat leave early...
So, another wasted day, wasted weekend (just slept the whole weekend basically) and friday and monday at home - not impressed with myself at all.
At least the baby is doing cossack kicks in my belly so hopefully that means nothing wrong in that department...