Also had a very good quote from venture. They do pascoe ribs for info. I've had tubes from henshaw before also.
Before you buy, think about warranty returns and the location of your fitter. Tubes do go wrong and dragging a boat to where ever is not as easy as returning a pair of shoes.
Other Solent ish tube companies include
Rodella ribs (used to do some Scorpion)
Other West Country tubers include
Ed ribraff, rib repair (very good prices)
Paul Tilley (well thought of on here)