I'm interested in booking the following flights:

24 Apr LHR-SIN
1 May SIN-LHR

When I try to book on ba.com, I get an error message just before the final quote page (doesn't matter which flights I select out of the four options, two BA, two QF). They appear to be available on expedia.co.uk.

I only get the error message on "economy - lowest", not on full fare economy or any other cabin (but lowest economy is what I'm interested in, unfortunately).

I've tried several times over the last week, on both my home and work computers, with no luck.

I wonder if anyone could try this, just to see if they can at least get through to the final quote page (I get the error after selecting the second flight), or provide an explanation as to why this is occurring (availability?).

Would prefer to buy direct through BA rather than Expedia, in order to get my miles bonus on the BA Amex.

Many thanks
PhilH