Hi, I totally understand where you are here! My son (now 4) was sat on the toilet before bath time every night from about 19months, at 1st he wasn't having any of it and ended up refusing/crying not to get on the loo before his bath. In the end we bought a "potty chair" that could be a potty in the living room (nice I know, but these things must be done!) and folded out to steps and a loo seat when he felt like using the loo. To let him make his own mind up where he wanted to pee was the best decision and he was dry in 4months!
My daughter on the other hand is 16 months now & telling me "wee wee" and whenever we go to the loo she stands outside shouting "Mama wee wee!" so Im thinking she maybe ready!
I think you have to play it by ear, place a potty in his bedroom, one in the living room and get a padded loo seat that comes off.
They all get there in the end, it's very rare to see a child start school in pull ups!!
Good luck!!