ALA/Pistonheads I believe only allow for 6 months from delivery but are pretty good.
Its definitely worth doing - the policy for the scheme on lease vehicles covers not only the gap between replacement and your car insurance, but also the balance of the lease payments to let you get completely out from under the deal (yes, you can still be liable for those!!)
Should be about £150 but use the pistonheads scheme to get 10% off with ALA.
Other insurers are also available, but ALA have a good rep.