Depending on which side of Manchester you are, I can highly recommend Mustang Equestrian near Chester.
Very good service and sturdy 3.5t stallion boxes. They do long trips.
Gillies Transport do regular weekly runs south from Scotland and are very good. I have used Parkers several times before and they are also excellent. Both look after the horses as if they were their own and are reasonably priced. Give them both a ring and ask for a quote. From memory I paid Parkers £480 one way from near Dusseldorf to here which was a 3 day journey with stopovers whereas when I moved my Connie from Somerset to here using a small local company it was over £350 for a two hour journey.