I’m surprised at the Roberts. I’ve got one of those cheap plastic Pure One Mi radios at work, which is a room with mostly steel walls, inside another larger steel walled building, and it gets a good signal most of the time, unless the transmitter is playing up, which it did today for a while.
Personally, I’d have a look at one of the supermarket ones, like Tescos or Sainsbury’s, pretty cheap, sound ok; I’m getting one soon for work, so the Pure can go into my other workspace without me having to take it back and forth.
Using your phone is fine. If you have unlimited data, and somewhere with really good signal strength and data.
You’ll use around 500Mb/week, using it for around 30-35 hours/week. That’s half the standard monthly data allowance, right there.