Go ahead and get yourself registered. Its most unlikely you will be poaching the boss's work. Either way it keeps you legal and gives you options for the future. Just don't be daft and use the van with the company logo on, you will be spotted, or pinch materials off the van, thats theft. Don't wear the company shirt either. If someone makes a complaint they will ring the company for sure..(seen it happen )
My old company eventually banned us from doing private work as a few idiots abused it. After that the only people regularly seen doing private work were the middle management types who were supposed to police it.
Just imagine if they walk in one day and make you redundant. If you have no backup you could be in real trouble. By getting registered and doing a bit of your own work you will be much better prepared. And get yourself some third party liability insurance as well. Simply Business (look em up on the web) are not expensive and it gives you peace of mind and your customers some protection.
Good luck and enjoy the new baby (those were the days eh ) Ah...no baby in OP's post..other advice still applies
Alfredo
What would you suggest in your opinion is the best way of getting some private work?