Talk to them? And raise it direct with the board as it's a Club partner.
I get this every year with all my insurances: home, car, van, public liability. They send you the "we've searched the market for the best price" letter. You then ring them and say "I can get it for half that". After a while they nearly always match like-for-like. They're just trying it on, and some people are too lazy to challenge them.
Locktons, though, aren't a broker. That's always been my concern: a broker searches whole-of-market for the best product, not just the best price. They were no use to me as their one-size policy included too many extras I'd never need, but I'd have to pay for. There's no "like-for-like" price you can quote them as they will always come back with "our policy is unique". Seems a circular argument to me: I want to be treated as an individual (number 6, lol), but their business model is all Porsche owners fit one product.