I know what you mean about crappy brushes MrsLettuce. I think the Body Shop ones are really good (not sure if they have a push brush). The brush I'm using is from Ruby and Millie and at least 10 years old, and was about £8. It's the same shape and size as the Mac one but the bristles are slightly longer - it's still v stiff and works for pushing. I think as long as you have a brush that's the right shape and the bristles feel good, not too fluffy or plasticky or soft, you'll be fine whether it cost £2 or £25.
Am liking the push liner a bit more today, but then I'm having a good skin day and look less tired overall, so that might be why.
I use the MAC 212 brush, and it's very good. I haven't tried other brushes in the same shape, so I have nothing to compare with. But the 212 keeps its shape after many washes and is stiff enough to work with, but not so stiff that it's uncomfortable.
Personally, I can't use an angled brush (I have MAC 263) to push the colour into the lashes. I can draw a line along the lashes with the brush and do a wing, but it's not the same as pushing the colour into the lashes.
I just tried it and I love it!! Peacocks have a brow kit for £5 - I used the black colour for my eyeliner. The brow colours and brushes ate OK too - a nice bargain! Quality wise its similarto my bodyshop brow kit - the peacocks one has morecolours too