Just found this:
Do not avoid registering for VAT by artificially separating business activities
If you run more than one business the sales in all those businesses must normally be added together to determine whether or not you must register for VAT.
However, if you are involved in the running of several separate legal entities, you may not need to combine the sales of those businesses to find whether you need to be VAT-registered.
If HMRC decides that you have artificially separated one business into smaller parts to avoid registering for VAT, it can decide that the entire business is a single taxable person and therefore must be registered for VAT. See the description of 'taxable person' in the section in this guide on who can and can't register for VAT.
Situations that HMRC may consider a single taxable person for VAT purposes include:
•Separate entities selling to registered and unregistered customers. The VAT-registered entity sells only to VAT-registered customers, and the entity not registered for VAT sells to customers who are not registered for VAT.
•The same equipment or premises being used by different entities on a regular basis. The premises and/or equipment are owned by one of the parties, who charges rent to the others. This situation may occur in businesses such as launderettes and takeaway food operations.
•Splitting up what is usually a single sale. This is common in industries such as the bed and breakfast trade, where one business supplies the bed and another the breakfast.
If you deliberately avoid registering for VAT, you may be liable to a penalty. For serious offences, the matter will be investigated and you may be prosecuted.
...and this:
It is the person, not the business, who is registered for VAT. A person can be either an individual or a legal person or entity. A registered person might be:
a sole proprietor
a partnership or limited liability partnership
a company
a club
an association
a charity
any other organisation or group of people acting together under a particular name, such as an educational or health institution, exhibition, conference, etc
Each VAT registration covers all the business activities of the registered person.
