I love the MT gisbornes they are really fabulous but closer to £50 however yesterday I found them on surrey equestrian for £35 and they are honestly worth it in my opinion. I wash and wash mine and they never bag or sag and they fit just right - are not too low on hips and not right up under boobs either.
Caldene ones are good quality and last well, also have zip pockets which I find really useful. I have managed to get some in sales cheaper but they are not ordinarily under £30. Thinkmy last pair were around £35, however my Belgrades were dearer, though if you can in the childs ones you dont pay vat, I did. Look at equestrianclearance.com.
Derby House Dakota Breeches - love them. Wash well and keep their shape, not worn a pair out yet. Warm in winter and cool in summer, belt loops and proper flies and a nice metal logo thingy hanging off one front belt loop makes them look a lot more expensive than they are. And only £19.99 a pair. Zip pocket is very useful for a mobile.