Partnership break up?

A husband and wife partnership have a retail shop and a workshop. They make their own products and sell them in the shop - all to order.  Apart from the usual business problems their main concern is business rates. The local council have added their 2 properties together (as it's the same business) and the business suffers a full rate charge - nearly £20k pa. The workshop is some distance away from the retail shop.

Considering splitting the business however concerns are a) probably not a sufficient business reason (?) and  therefore VAT office wouldn't be happy?  b) the workshop only carries out work for the business - unlikely to do other work but this is an area that would be looked into  c) the retail shop couldnt carry out other business as it would defeat the object of having a footprint on the high street for their core products  d) unlikely that they would bring another individual into the business  e) if a separate workshop business only carried out work for the separate retail shop - would that be a problem - probably back to point a) as a separate retail shop would rely 100% on the separate workshop business to produce its goods for sale!

would welcome any thoughts on this - or are they stuck with the single entity !