if you are buying pot grown plants at this size they will be fine. Beech needs regular 1/2 times a year to really keep it compact and with leaf the full length of the stems. They are quite a thirsty hedge so done expect to grow too much within at least a metre of the stems.

If budget is a consideration you can buy bare root at the size described for way less than pot grown specimens.Also as beech are reasonably fast growing, smaller plants will form the required hedge quickly if looked after for the first year or two.

Smaller plants will establish more quickly. If you go for height straight away it may be harder to get leaf cover right to ground level. I certainly wouldn't plant ones as tall as 1.5metres. Patience is important when establishing a new hedge.
We only cut ours once a year in early autumn. Leave enough space from the boundary as with time it will get quite wide. It makes a lovely hedge - ours is beautiful just now as its a mixture of green and bronze.

Most good garden centres will have bare-rooted beech at a reasonable price now, so you can afford to plant thicker or even zig-zag. I have read that carpinus (hornbeam) will do better if we are to experience global warming, as they do better in drought conditions.

They don't keep their leaves all winter though do they? But I guess they'd still make a good screen if the hedge is nice and dense.

beech hedging tends to retain its bronze leaves and shed them bit by bit through the winter. makes tiding leaves a real pain.

Thank you to everyone who responded. I think I will opt for beech about 1mtr high. I know it will loose cover through the winter but as it's in the lower part of our garden & we aren't often down there through the winter, certainly not sitting out, I feel this is acceptable. For so long I've admired other peoples beech hedges and think this is my opportunity to have one of my own.
Thanks again and happy gardening. Jenko.

Seaburngirl, I hadn't noticed it shedding through the winter - but it is so windy here that the leaves probably blow away before we notice them! There are still plenty left by the spring though.