Best price: £4.99 (Halfords.com)
Capacity: 400ml
Diameter of base: 61mm
For: Ergonomic handle
Against: Mediocre performance; not watertight
Overall::
Performance: 
Mediocre performance and cheaper cups retained heat for longer. After two hours the temperature inside the Halfords cup had nosedived to 46C.
Ease of operation: 
Twist the centre of the lid to open the drinking hole and take a sip. We liked the size and shape of the plastic moulded handle, too.
Buying:
Available from Halfords only, so there’s no chance of sniffing out a better price. If you don’t want to spend more than a fiver, we’d go for the Draper Warming Mug instead.
Quality:
Had a plastic outer case similar to that of the more expensive Thermos Travel Mug. Seemed fairly solid, apart from the brittle-feeling handle.
Special features: 
None. Available in blue.