I've got some very recent experience with Planet Ice. I've been to Altrincham recently, a decent enough rink, if a little shabby in parts, but I go to Planet Ice in Widnes for lessons.
I have an Ice Card, so I get a little discount (worth getting an ice card if you go regularly). With that I've book a block of 4 lessons for £41, half hour each. They are group lessons but my group was about a max of 10 people. Lessons are well taught. I don't know how good a skater you are, but you may get stuck on the simple Level 1 stuff if you can't stop, so lessons are kind of a waste of money until you learn how to stop (my current predicament). Coaches are friendly and helpful.
I do have my gripes about Planet Ice though. They charge £2.20 for spectators which is a total joke. Even more laughable is that if you have you own skates they knock £2.20 off, but then you need to use a locker to store your shoes which is like £1, which you don't get back! They literally look for money from you wherever it can be found.