when shipping goods out the UK they will either:
a) get you on weight
b) or on size..
what i mean by the above is that, whatever is higher either volumetric weight or gross weight will be used to calculate the charges...
You could try calling interlink who are very reasonable, fed ex (kind of expensive) or DHL...
Tell them the following measurements:
height, width, depth and put it on their slowest service possible...
hope that helps...