Re the Singapore Airlines flight, while there's no chance of bagging it for £185 now, I've kept my eye on it and the prices have been fluctuating on various sites. I did a fresh search about an hour ago when I woke up and found the following:
Opodo - £264
Singapore Airlines own website - £260
Lastminute.com - £251
This is back in my ballpark so I've taken the plunge and finally booked it through Lastminute.com. I'm not sure how many spaces are left at the above prices but I thought I'd post the latest situation for anyone still considering booking on this flight.