Are there any YouTube videos you can recommend for tips on technique?
I've seen some good ones, but I haven't kept links to them, sadly. I'd also recommend having some one-to-one lessons with an instructor. Don't let anyone teach you crawl breathing on every fourth stroke - it's much, much easier and better to breathe on every third.
When and how often do you swim?
Every day, if I'm in staying in a location where this is possible.
How do you look after your hair? What hairstyle do you have? Do you use expensive shampoos? Are you constantly drying and styling your hair?
I don't bother doing anything special; I don't even use conditioner. I have shortish, naturally curly hair. I wash my hair and let it dry naturally. It looks fine - I think maybe I'm just lucky. I sometimes wear a hat, but I have phases of getting fed up of the hat, and just putting clips in my hair instead, to keep it out of my eyes. Swimming hats don't keep your hair dry, but I think they probably stop it getting absolutely drenched with chlorine.
Do you have specific workouts you follow or do you just do lots and lots of lengths?
I mostly do lots of lengths, but I do different strokes in each session, unless I'm swimming in the sea, where I do only breaststroke with my head out (I've never managed being able to swim crawl in the sea). I do a mixture of gentle swimming and pushing myself harder for fitness. Sometimes I do a few exercises in the water.
How do you keep water out of your nose when doing proper swimming?
Breathe out gently all the time your face is in the water. The air coming out stops the water getting in.
Do you do other forms of exercise to keep fit too?
Running and standard exercises like stretching, sit-ups, press-ups and weights ... not as much as I ought to do, because I only really like swimming as exercise. I walk a lot, too.
Are classes like aqua combat any good?
I've no idea, as I've never done one. What on earth is aqua combat? It sounds scary!