Fantastic lens but the cost is a lot. USA £7800, UK£ 12000. Over a third more expensive. Ouch!
See it from the bright side, you can do a weekend trip to New York, live in a swanky hotel and eat nice and on the Saturday pick a lens up from an actual shop stocking it while still saving money overall.
That price differnetial isn't the fault of Canon....they base price to the dealers is pretty much the same. It's juat a bit of blatent profiteering from the UK vendors who are selling at full RRP and think they will sell every copy they can get their grubby hands on.
At the current price differential, get a standby flight to the US and go and get one Stateside. It'll cost you time and energy, but will yeild a serious price saving.