Well quite honestly I wouldn't have either. Leylandii is a thug and laurel is best pruned with secateurs so can be a lot of work - it also gets quite wide. Had you thought about Lonicera nitida? There is a golden variegated one that's quite bright and cheerful. You can cut it with a hedge trimmer and done well it makes a solid wall. It doesn't grow as fast as leylandii or laurel but it isn't as much work to look after and I think it is much neater for a formal front garden hedge. Have a look at Google images.

If, by 'laurel, you mean Cherry Laurel (Prunus laurocerasus), that wants to get 25 feet high (nearly 8 metres) by about 12 feet, so its a lot of work trying to keep it in check. If you actually mean Spotted Laurel (Aucuba japonica) that won't make the height of 2.5m you require and does, indeed, need to be trimmed with secateurs. As for leylandii, there's only one way to plant those, one in Scotland, one in Ireland and one in Wales - costs an arm and a leg to keep it as short as you want, given it wants to get up to 100 feet.

I'd suggest Berberis darwinii instead - yes its prickly, but it reaches just under 2.5 metres in height, and you can trim the sides a couple of times a year, so you're not constantly fighting with a plant that's too large for the job.

If you're ordering bare root hedging plants, have them delivered in late October if possible - prepare the ground properly in the meantime by digging it over well and incorporating composted animal manure, if you did not do this the first time round. Any reputable supplier won't send out bare root plants other than October through to end of February/early March anyway.

I recall your privet plants were planted in March this year - its always best to do it in autumn if you can, then they've got the winter to settle in without suffering from drought. Will need watering during dry spells from spring onwards though.

Not a fan of either Leylandii or Laurel, infact Thuja is better behaved than Leylandii. As suggested berberis Darwinii would fit the bill. We all have our favourite hedging plants and mine would be Yew (Taxus baccata). Would not be a beast; can be trimmed into a formal and neat hedge and has few enemies.

First of all, why do you want a hedge of 2.5-3m high?

How have the privets failed - all 15 together or in ones and twos? How far apart did y plant them, when and how did you prepare the planting area?

Once you've sorted out what the problem is - which you can't do without reviewing what you did - you can make a proper judgement on what to do next - which really should not include either laurel or Leylandii.

You could use the gaps which have been left by the failed privet to introduce native hedging that might help wildlife and won't suck the life out of your garden.

Bamboo just because you live in England is no reason to wish leylandii only on Wales Scotland and Ireland...

Heh heh, sorry... figured we'd got enough of the blasted things here already;-))