1m range sounds a little short but about right Rotty and is about where your expectation of a 2.5kw lamp should be. You need to position it above the table or seating, if I put mine next to the table facing down, the heat is strong for everyone sat at the table, too much at the side of the heater if anything.
if you need to heat multiple spots then you’ll need multiple heaters, they are cheap enough to run and non intrusive that you can easily do that if you wanted to.
If your expectation is to heat a large area like a blanket then you’ll need a lot of power, which will burn a lot of gas. The gas ones in perspective can be 20kw or more...