Ms T
Honey-coloured ramparts
They're not just about getting someone to shout at you to get off the couch, they can show you where you're going wrong with technique in various exercises, show you when you're pushing parts of your body too hard, when you're not pushing hard enough, help you avoid injury and if you're short of time they can help you get the most from your workout.
^^ This. Nothing wrong with hiring a personal trainer, if you can afford it. I am too tight-fisted, personally, but I find classes are great at pushing you a bit. Plus you have to book into them and are supposedly penalised if you don't turn up (at the Lido - not sure this actually happens in practice). Hendo used to have a personal trainer (also at the Lido). He was excellent, but the prices went up so it became a bit too expensive. I think it was something like £40 a session if you booked ten, so £400.
And yes, we have a cleaner as well. Judge away.