In terms of stats, mechs from the UK tend to be rather eccentric, and even backwards at times. Having very high or very poor ratings in various categories. For example, Longshanks has great armor, but very low speed and mediocre payload capacity. While the Isambard has great speed for a medium mech, but lousy armor.
One consistent advantage of British mechs is a slight edge in terms of storage capacity.
While their mechs are not always spectacular, their mech weapons put up a very good show - much better than the American options in the anti-armor department. Very good hitting power and penetration. British made melee weapons are highly nostalgic and celebrate a very medieval flare; maces, swords, axes, lances,