On Sat, 15 Dec 2012 15:28:20 +0000, John Rumm
wrote:
The price of swapping the RCD will be lower than any other option...

I'll be changing the RCD anyway. As you say, it's a cheap option. I
just wanted to see what difference it had made. In the past, I've made
changes and thought the problem cured when months went by without a
trip, only for the RCD to trip six months later.

You could always grab one from ebay, use and re-sell.

Yes, that's a possibility.