I can understand stopping you running as your 2nd claim club when you're in a closed club series of events where your 1st claim club is running too. That makes sense.
It doesn't make sense stopping you running as either club you choose for a random open event, that may give a team prize, but isn't aS such a closed team series.
For example, running the local 10k last year, it made sense to run as my local club, rather than one 40miles away, as plenty of the local club were running.
I suppose unless you're either pretty well known (like Ben!), or have a snitchy team mate (like me) you can get a way with whatever 
ps don't get me started on the rulebook for changing 1st claim club.
How on earth it's legal for the original club to in effect "Hold" your registration even when your year's membership has run out I'll never know. They don't pay you, so you should surely be able to change 1st claim club tomorrow.
Instead, you have to get sign off from both clubs, pay a fee, and face a potential ban!
ps Sleepy, the league Ben should have raced down here was on a saturday. Probably similar to what you're describing there. Segregated races based on gender and age, and longer distance for the men. Higher standard too at the front.