no point hiring a solicitor, bang to rights as far as I can tell. Just go, look contrite and take what you get. Won't be too serious as you didn't actually cause an accident.
With dual carraigeway slip roads the art is to merge seamlessly, you should not stop unlkess abolutely necessary, that'll get you a due care too, but you should match your speed with traffic on the main carraigeway and sort of drift into a gap at the same speed as the prevailing conditions. Those already on the carraigeway will (should) also apply the merge technique when they see you are "playing the game".
It's a pity that this sort of thing is never taught prior to the test, bikers learn this and all sorts of other road craft.