Hi,
I have had them swim around me whilst scuba diving off Sanda and on one occasion i felt a tug at my leg, turning round a seal was playfully biting on my fins, i had a camera and took a picture but the flash frightened it off, unfortunately the picture didnt come out very well.
I think they swim with you rather than the other way round and are easily frightened off, so dont know if swim with seal trips would work. When we drop in the water nearby a reef they tend to disappear underwater, they are great to watch underwater and really graceful and agile.
In the Farne Islands where there is a lot of scuba diving they are a lot less wary
Look at some of this guys videos, some amazing encounters in the Farnes
http://www.youtube.com/bburville#p/u/1/uXpalZJ3QgE