Royal Mail are releasing various stamps on 14th March
Available to order here https://shop.royalmail.com/special-stamp-issues/marvel?iid=SC0219_MARV_DD_14 , in local UK Post Offices and most probably eBay
Available to order here https://shop.royalmail.com/special-stamp-issues/marvel?iid=SC0219_MARV_DD_14 , in local UK Post Offices and most probably eBay