I've found quite a few nurseries selling Tolmiea menziesii by searching for 'Taff's Gold' (which is one of its many names). However most of them don't seem to offer mail order.
If you happen to be near Leeds, try here:
http://www.millrace-plants.co.uk/plants-search .asp?searchterm=taff%27s+gold&Submit=Search
If you're around Essex or Cambridgeshire, this might help:
http://www.beechesnursery.co.uk/
This nursery is in Suffolk. It does offer mail order but there's a minimum �15 order and �10.50 carriage:
http://www.shrublandparknurseries.co.uk/
This is in Gloucestershire. There's an indication that the owner might be persuaded to accept mail order:
http://www.hoohouse.plus.com/loading_page.htm
If you get really stuck, send me an email:
[email protected]
I live just down the road from Shrubland Park Nurseries, so I could buy a plant and mail it to you.
Chris