Repeat Meeting in Different Location

In summer 1970 my family and I had had a disastrously bad weather experience camping in NW Scotland and were taking a week at random in South Wales as compensation before school and work began again. We did not choose the camp site at Llangennith but were forced by earlier choices being full up. The only suitable pitch for our rather large tent was next to a family which was just beginning to pack up, and, after we were established, we offered to give a hand, as campers do. The fellow asked what I did and when I said I was in the RAF asked if I knew so and so. Surprisingly, I did, (at the time there were only about 180,000 in the RAF so it was quite a good bet!) and we chewed the fat about this character whom we both admired as it happened. As evening fell we said farewell and withdrew to our tents knowing we wouldn't meet again because the man and his family were off very early the next morning bound for Manchester on their motorbike and sidecar, a vehicle which was more common then but which was still unusual. The following year I was posted from Southern Scotland to a different Station in Eastern England and coincidentally (ho, ho!), we needed a new tent to fit the growing (in individual size) family of 6. Whilst staying with in-laws for Whitsun 1971 the intention was to buy the new tent in Bristol and try it out on a site owned by the tent retailer on the Mendip Hills nearby. Their staff helped us put up the new edifice and just as we finished there was the roar of a motorbike exhaust and a combination swept in right alongside our pitch with a flourish. We looked across and to our amazement and theirs, there were our acquaintances from the previous year at Llangennith, just taking off their helmets and dismounting. After all the bafflement and disbelief was over and we'd got re-acquainted, we heard that it was by no means planned for them to stop at our camp site. They were trying to find the road to the top of Cheddar Gorge without a map, had got lost and had turned in to our site in desperation as dusk was falling. We were also there by chance, not knowing, when actually buying the new tent in town, that the retailer had a site on which we could try it out. We, too, had had vague ideas about staying somewhere near Cheddar, but had made no plans. We have never seen the people or had any connection with them since. What kind of a coincidence is that, and what are the chances against it happening?