Firstly, if possible, travel by Eurostar (rather than flying) and take as much luggage as you can with you. Eurostar allow you to take two pieces of 'average suitcase-sized' luggage (with no weight limit but not longer than 2m) and one piece of hand baggage, without charge. Additional bags, up to 30kg, are charged at just �12 each. (That's far cheaper than any airline or shipping company would charge).
For items you can't take with you, try UPakWeShip:
http://www.upakweship.co.uk/
Chris