Have you pruned them at the wrong time is my first thought...then, Hydrangeas prefer a sunny position, and like lots of water. Lastly, what are you feeding them? It could be that the feed is helping them produce lots of leaves at the expense of flowers.

Thanks for reply......They are against a south facing wall and get full sun from about 10am onwards; We've been feeding them a general 'shrub/tree' fertilizer. We also water them well every/every other day.
We have geraniums alonside them, they receive the same watering regime, and they have flowered abundantly all summer...

next year you will have flowers
do not prune them till they flower

I've had a few for around 3 years and they've never flowered. I put it down to the last 2 severe winters, thought I'd lost them but managed to survive and now lots of leaves but no flowers.

Try giving them a high potash feed next spring, to encourage flowers rather than greenery.

Thanks Steve ..... so Tomorite would be suitable then?

Yes, but it would be better to get some sulphate of potash powder and put it round the shrub as a dressing in the very early spring. However next years buds will probably all be decided on by then, but it would probably help for the following year. Maybe someone else would be able to tell you whether there would be any point in putting it on now, as its not a general fertiliser and wouldn't encourage new green growth too late in the season.

Hi Stera, thank you. It will only do good, I'll get some :)

On second thoughts its highly soluble, so in winter it might just get washed out of the soil before the bush could use it. So even if you add some now I'd put another dose on in late winter or early spring. I put it on my gooseberries in late Feb.

Expats, Geraniums (Pelargoniums) need a good deal less water than Hydrangeas, so watering every other day may be keeping them under constant water stress. If they are wilting even a little between soakings, that will kill any incipient flower buds, even though the leaves will show little damage when they recover. Pruning before they flower can also be a disaster, since they bloom on the tips of last year's growth. If your garden has shared the ferocious winters of the UK of the last two years, that may also have done "pruning" at the wrong time of year, also.

Thanks Stera, I'll apply late Feb too.

Hope it works for you

Me too, if I get flowers next year, I will let you know :-)