How long have you had the plant? Have you ever pruned it, and if so, when? In a pot or in the ground?

It is in the ground and I have had it about 2 years. I pruned it last year and only had 1 flower head so I left it this time but now I have no sign of any flowers at all.

I think it may be a bit early for flowers to be showing. I have one and there is no sign of buds yet, but if I remember correctly it flowered a bit later in the summer last year.

Okay, but precisely when did you prune it last year, what month? Most hydrangeas flower on the previous year's wood, so if you pruned it, say, last summer or autumn, you pruned off the wood which would have produced flowers now. Only pruning required on this type is in April, as growth begins, and at that point, you cut out anything obviously dead, and nip off the deadheads from the previous year and any dead tips. And that's it...