To tell you the truth, it should not be a problem, some people have no choice, and have to place a sofa in front of radiators, I have mine about 10" in front of a rad, my room acquires an even temperature, no hot or cold spots, one reason for this is that I keep my heating on 24/7 throughout winter months, but run it at a very low temperature of like 35- 40C flow, or in cold winter where outside temp reaches close to Zero, then may be I run it at 50C, right now it is running at 50c, and my place is warmed up to about 21C in all rooms. ( Probably not needed this high)
( as for leather sofa, it has not suffered any deterioration from the heat, since 2003, except due to sun light, (south facing) its colour has slightly faded)
The rad I have in my living room is double and sits under a bay window, so is shaped to fit a bay window, so its overall length is 2.4m, and is 400mm high (Double) and at night I draw my long curtains and tuck them behind rads so as to stop heat from the rads going straight up behind them and out through cold window panes! (DG) on top of this I have another rad in the 2nd part of my through lounge, which is 1.3m x 600, double.
Edit:
I used to have a double 1.6m by 600mm radiator in my front passage which is 6 foot wide and about 18 feet in length, and has stairs to go up, I took this rad out about 10 years ago to have the walls skimmed, and it never went back in again, and it has made absolutely no difference to the warmth you get when you step in my house from outside, you feel as if the passage is heated well, and not only that heat from through lounge and from kitchen/dinner where there is just a single 1.2m by 600mm rad is enough to send so much warm air towards upper floor and upper passage where I do not have any CH except in just one room i sleep in, where I said my bed is covering half of it. Main reason would be since I heat my house 24/7 so it stays warm all over evenly with maximum temperature difference of just 1 degree celcius.