Realistic toy guns are banned in the UK.
Based on the information on that page, it seems quite likely that this would qualify and therefore be banned. The penalty for trying to import it could be up to a £5000 fine or 6 month prison sentence.
This mainly hinges on whether this gun is considered "realistic". In the U.S. an orange tip on a gun is sufficient to mark something as a toy, but here is the relevant guideline from UK.gov (emphasis added):
an imitation is to be regarded as distinguishable if its size, shape
or principal colour is unrealistic for a real firearm...
An imitation firearm which
is principally coloured bright red, bright orange, bright yellow, bright green, bright pink,
bright purple, bright blue, or which is transparent should...be regarded as unrealistic
In addition, the controller is styled similar to a real gun and is of sufficient size (longer than 70mm) to qualify as realistic under the regulations.
Beyond that, I would not ask a friend to bring something that is likely to attract the attention of security. Even if it were technically allowed, surely this is likely to attract attention and add extra hassle to travelling.