Just doing some general Amiibo browsing and went to Argos. I looked at Marth and it's let me order one with next day delivery. £10.99 with £3.95 delivery. There is also the buy 2 and save a few pennies offer mentioned elsewhere on here. They also had Little Mac as well. For info I live in South East London/Kent. It also showed up they had Marth in stock at the Erith branch and Wii Fit trainer is in stock at Bexleyheath.
Hope this helps people.