Cutting back new buddleia/lavender

I've had to plant a new buddleia & have replaced most of my phlox with a couple of young lavender plants. To keep them all in tiptop condition, how am I best pruning them when the time comes? The buddleia keeps sprouting new flowering heads but the lavender has more or less finished by the looks of it.
The lavenders are about 12" high and the buddleia is about 4'
Thanks

 

The Buddliea you can keep snipping off the spent blooms down to the next leaves and hopefully with the sunshine you'll keep getting a few more flowers for a bit longer then I'd just trim it on a level with the top of the wall when it's finished to save any wind rock over winter then come next spring I'd cut it back to 2ft
The Lavender I'd cut the flower stems off down to the leaves and maybe just a little off the top to keep them in shape but not into the old wood

I'd then cut the heads off the cut flower stems and put them in a jar of caster sugar,seal and shake once in a while...Lavendar sugar lovely in shortbread or cakes

 

I'd cut them harder than that, only leaving one or two pairs of (current year's growth) leaves on each stem. You can be less harsh if you want the plants to establish larger than that, but once they get to "desired height" you definitely need to be that hard on them - but don't actually cut back into old wood. If you don't cut them hard enough they grow leggy and flop over and look a mess ...

 

Thank you both
I didn't know how harsh to be with them only being young plants. The lavenders I'm not overly fussed about being tall but I would like them to eventually fill out nicely horizontally

 

I'm not sure you will be able to get them to do that ... when they get a fair bit of weight on some, relatively, long stems they will flop ... "dome shaped" is the most easily achieved, and that is done by being brutal with the pruning after flowering. Best to read up the technique on a specialist Lavender grower's website, e.g. this one (it starts a paragraph or two above this link):

http://www.downderry-nursery.co.uk/lavender-care/#attachment_747

 

Thanks for the link I just know I don't want woody bushes down the line with only a few flowers