Hi Big norm, Carriotjuice is correct that the transfer eats a load of miles when you exhcange.

My question would be where are you intending to use the miles? If you are UK based then it might be worth sticking with Virgin as at least you'll have more options for earning and topping up than you will with KrisFlyer.

You can transfer UK Amex points to KrisFlyer 1 for 1 and it usually only takes a day or two if you need to top-up (just did it last week myself). Aegean is not a partner of Amex UK so you won't be able to transfer points. You'll need to hit a status level to get lounge access.

If you are trying to use the Aegean loop-hole note that they've changed their program which will be going into effect from late November - see this other FT thread.

Also if you do opt to fly with Singapore Airlines and are booking cheap discounted Economy tickets they've reduced K class earning rates to 10%, Virgin Atlantic still states 100% earning rate for that class.