How many people do you want to use the phone at the same time? With just one line you can receive and make just one call at a time.
The running costs could be higher but personally I would go for 2 lines into your house - 1 for business and 1 private (ex-directory). You will also find it much easier to separate out the costs of business and private calls.
A lot of people don't like "press 1 for", etc.
Personal view - others may differ.