I have very thick, wavy long blonde hair. It goes quite bushy and frizzy. I have to straighten it to go out anywhere nice; otherwise I tie it up as I run a pet care service mainly dog walking. I really want a change and I love the mid length tapered up from front to back look, bit like Rihannas in Umbrella. Would my hair take this without constant straightening and would it drive me mad out in all weathers dog walking?

To be honest, yes. Although the style would look great when you straighten it, if your hair is naturally wavy and thick this style does take a lot of up keep and would not look that great if you do not straighten it. You could try having a chemical straightening process but I would strongly recommend you have a consultation first.