I'm pretty sure the "routine checks" is a pile of crap
I think they have to have "reasonable grounds" see here:
http://www.yourrights.org.uk/your-rights/chapt ers/the-rights-of-suspects/police-powers-to-st op-and-search-persons-and-vehicles---without-a rrest/index.shtml
I wonder if you happen to look a bit like someone they're after
Of course that doesn't help because it's easy to come up with something. I've had "your car seemed a bit low to the ground" and "you have an intermittantly defective rear brake light" is also a stormer!
Having said that although I was stopped a number of times (but nothing like your figure) that magically seemed to stop after I got to about 30!
I'd follow nox's advice, you'll probably get a polite reply informing you about all the good things that they are doing to protect you and how they don't use crude profiling and that you've been unlucky.
They'll then probably send out a memo saying "pack it in boys"