I think you need to work out exactly which cooker you have. See the range here:
http://www.rangemaster.co.uk/products/range-cookers/classic/classic-110-dual-fuel
Looking at THIS dual fuel version suggests you need a 230V supply capable of delivering 7.2kW, which is way more than 3A and would require a proper cooker supply, let alone a 13A outlet
http://www.rangemaster.co.uk/media/332747/u110110-06.pdf
Looking at THIS one still suggests you need a 230V supply capable of delivering 2.6kW, which is still way more than a 3A fuse will allow but within the bounds for a 13A plug, when fitted with a 13A fuse - not a 3A one.
http://www.rangemaster.co.uk/media/992252/u110117-07.pdf
May one politely suggest you get someone to check your installation - someone who knows what they are doing?
XXX
January 2016