I would think that Halfords would be able to order you a replacement key socket (they are an official McGard dealer) as you have the necessary code available. You would only have to resort to ordering direct from McGard if you don't have that as they would identify the patten from you sending a clear photo of the locking nut.
There is also a UK website which offers a replacement key service for £45.99 (lockingwheelnutkeys.co.uk
), who will use the security code and an image of the nut (to verify that the code matches the right key). I have not used them, so can't offer any specific recommendation.
I have to say that £60 does seem a bit extreme - I needed a replacement key about 4 years ago (for a set for which I didn't have the code) and ordered one direct from McGard in Germany, and it was £16 including shipping!
Regarding removal without the key - I think the best option would be to visit a reputable tyre supplier as they often have suitable tools to remove locking wheel nuts. Are yours the type supplied by MG Rover from 2004 onwards? - these have a security collar around them which makes removal without the key more challenging. However, MGR only used a limited number of the available patterns, and all the dealers should have had a master set of keys; if you have an ex-MGR dealer or an MG Rover specialist locally, it might be worth asking if they have the master socket set (from memory, I think there were about 16 variations).
When a brand new set of McGards including the key is under £40, I wouldn't think most people would bother spending more than that for a replacement key.