Stone in caliper? Bearing?

I've recently discovered the joy's of getting stones stuck in the caliper. The first time I heard it I thought something was seriously wrong!!! Anyway, since my mechanic explained it to me I've been less worried about it when it happens. It happened again this morning, so I just carried on as they tend to grind down and fall out but it's not budging this time!! Driving around 35mph and all of a sudden the defender veers a sudden left!!!! If I was going any faster that would be really bad. I'm thinking this is more than a stone. Any suggestions? Bearing? It's also developing a low rumble sound now too. (After about a minute or so of driving).

youll have to jack that side up and have a look,feel for play in the wheel then remove wheel and look at the brake

Sounds like a wheel bearing has gone. Get it sorted ASAP, it won't last long before it welds itself, if it hasn't already, to the stub axle and becomes a PITA to fix.

Thanks, yeah I'm worried it's the bearing. Going to get the recovery company to take it to my mechanic asap!!!