First up, I would just like to say that if you are with Nat West, then there id a very good banking app available for WP, as well as Halifax and RBS, so this article may be somewhat misleading.
I switched to a Nokia Lumia 620 from Android (Samsung Galaxy SII) because I was looking for a cheap, temporary replacement for the remainder of my contract... My Galaxy SII having come off second best in a headbutting contest with a wall... I was intrigued by the simplicity and of the UI of a Windows phone, so I thought this was the best time to give it a go.
It wasn't until a month after getting the 620 that I realised just how frustrated I had become with Android. Yes if you love tinkering with stuff and are obsessed with having 3 different iterations of the same apps then Android is perfect. But, I didn't realise that I had become accustomed to having to power cycle my Galaxy SII (Turn it off and back on again) and that it freezing up was just part of having a phone...
Having a Windows phone was like a breath of fresh air to me, all the apps that I wanted are available and I don't have to use trial and error to make sure that the app I am downloading is any good or may freeze up what was already a temperamental OS. The Nokia Here apps are great and I have used these more times that I ever thought I would. I have Office 365, free of charge. I don't need Dropbox as I have Skydrive, and again I have found that I use this more than I thought I would.
Needless to say, I have preordered the Lumia 1020, on O2, with 64Gb storage and accessory pack which includes the wireless charging cover and wireless charger, camera grip and a mini tripod.