A couple of years ago, the Jockey Wheel clamp handle screw sheered just as we were setting up. Fortunately we weren't too far from Grantham Caravans where I was able to get a replacement, and a B&Q where I got some HSS drill bits and a stud extractor set to remove the half inch or so of screw which remained in the clamp. I now carry these, and a spare clamp handle in my tool box, just in case there isn't a caravan parts place within easy reach.
On our most recent trip, when we arrived at Hawes we found that the Motor Mover had failed (it was working earlier that day when we left Southport). I managed to reverse onto the pitch, the old fashioned way. A call to Truma diagnosed the issue as being the electronic control unit. I was able to order a new one and have it delivered to site next day (not cheap!). I have now found some places which will repair these electronic control units, and I'm seriously considering doing this, and carrying the repaired unit as a spare, in case a similar situation ever arises again. I suspect I'm being too cautious, but............