Cant comment on Lowther, because i've never been, but i've been to the Midland loads of times, i've never camped up there, but i always go up on the Sunday, and i really enjoy walking around all day looking at the various stalls, there might be some crap stalls, but there are also alot of good stalls.
I dont buy any of the food or drink up there because as people have said it's a total RIP OFF, one thing that pisses me off though is the entry fee going up every feckin year, and extra if you go on the Sunday, i asked a steward one year why it is dearer to get in on the Sunday, his reply was