Thanks for the replies. I'm leaning towards EK at the moment due to the transfer at Heathrow not being recommended!

Have flown with EK a few months ago and yes, whilst the 3-4-3 is more cramped than a 3-3-3-3 layout sitting down for so long isn't comfortable either way... and at least with EK's service via SIN it breaks the journey into three 7 hour segments and avoids the long 13 hour single flight.

Also the return from AMS works better for me... jet lag wise.