Happens all the time around Sheffield, I think they were high when they planned the roads/markings. There'll always be idiots who don't let you in, depending on how busy it is: stop and wait for someone to let you in (ensure you assert yourself by very slowly crawling towards the other lane, look at the oncoming drivers in the eyes), or if it's too busy - take any other route and try and get back round.
Alternatively, do what Giddy said, shove it into 1st with high revs, wheelspin your way into a space, ensure you "flash the V's" to the suckers who just got burnt out behind you.