I don't think many of the responses are completely relevant.
The OP has not told us when his main honey flow is that he is seeking. In Manchester it may actually be the balsam round all the old waterways, or he might be moving his bees late to the heather on the moors.
Timing is everything, and in the case of late season flows, early splitting MIGHT actually be the way to MAXIMISE your crop. Two colonies peaking can be a lot better than one colony coming off the back of a protracted spell of instability.
So.......more details needed......and happy to advise off forum if wanted.
Do not fuss too much about buying in a queen or two each season as suggested by others. Its not very fashionable on here to say it but it can be very good for the vigour of your stock to maintain a bit of genetic diversity.