Thanks so much for your concern. The vet said Bert had some discomfort in his right front leg, but he's unsure why. Has put him on painkillers, and if that helps then the stiffness has been down to pain (could be from anything, a virus, a muscle injury). The test comes when he finishes the 10 days course of Metacam - if the stiffness returns it's more likely arthritis and he'll need an Xray and some blood tests.
If the Metacam doesn't help the stiffness I have to take him back in 4 days for an Xray and some blood tests.
The vet, like me, was amazed he'd had a tick bite. It was snowing here again today, and freezing cold - they don't usually come out until it's warmed up in spring. He said Lyme would be very rare, but not beyond the realms of possiblity where we live.
I'll let you know how he gets on. Thanks again - I love this forum, everyone is soooo helpful and nice