As an example, say you own a property portfolio, (six properties and above), and you want to put them into a Family Investment Company, that will constitute one company.
Now let's say you also own a few million pounds of investments; we would recommend not mixing investments and rental properties. The issue with mixing them is, if you were successfully sued by a tenant all of the assets of that company would be potentially liable in that in that settlement.
It is safer to have two companies and keep your assets separate. The downside is you have got to pay accountancy fees for two companies rather than one, but that is a small price to pay for the safety of keeping all of your investments excluded from your rental property portfolio.
In conclusion, you can have more than one company and we would certainly recommend it in certain circumstances.