If I read your post correctly you are operating one sole-trader business and plan to start another sole-trader business. Is this correct? You mention "companies" which is confusing since that normally is taken to refer to a "limited company". A sole-trader business is not a company.
If I read you correctly then you need to be careful on the VAT front. A sole-trader can have only one VAT registration themselves. A person may own several different limited companies each with different VAT numbers but not if operating as a sole-trade business.
The problem can come from the rules applying to the VAT thresholds. €70,000 for sale of goods and €35,000 for services. If you are considering two business each consisting of sale of goods, then unless one of them is a VAT exempt activity then the €70,000 or €35,000 turnover threshold refers to turnover from the aggregate of the different businesses. So running two busines as a sole-trader, both of sales of goods and both normal VATable activities, and each with turnover, say, of €50,000 , then you would have to register as the total activity falls over the threshold.
This gets further complicated in cases of services and sales of goods. Unless all the business consists of at least 90% sale of goods, then the LOWER threshold of €35,000 applies. Say for example a hairdresser with turnover of €30,000 also has a business selling stationery with turnover of €70,000. Each is under the respective thresholds for services and sale of goods but in aggregate the % of services to total is 30% (30/100) and that means that both businesses must account for VAT.
Remember it is the person which is classed as a "taxable person" and not the individual business when operating as a sole-trader.
( all figures above refer to the VAT registration thresholds as at 06/03/08. The thresholds increase to €37,500 and €75,000 for services & goods respectively from 01/05/08 )