Because they come from the UK they are different in character to Coopers kits. However, being a 'specialist' line, be aware that they may have been hanging around a LHBS for a year or more. The only Muntons Kit I tried was one of the "Toucan" varieties, Best Bitter IIRC, and it turned out like bitter black molasses and was not a pleasant beer. I should have checked the best before date but I reckon it was well out of date.
Liquid malt extract darkens over time, and especially if kept in a hot Queensland Storeroom for months on end. This one was as black as the ace of spades.
I expect a fresh Muntons kit is fine, suggest check BB date and only buy from well run looking LHBS.