Hi Edm1, have you looked at some of the baby classes on Mumsnet? On our offers section Baby Sensory Knightswood have a special introductory offer. http://local.mumsnet.com/glasgow/offers I'm not totally sure about ages, but I think the massage is pretty much suitable from birth. I don't know about sensory or yoga but I would imagine they are similar!
Baby sensory is from birth so would find out about a class near to you and see if you can go along for a trial and make up your own mind on whether your LO is ready for it x if you go to www.babysensory.co.uk and use the find a class function it will tell you the nearest class