Second phone?

I have a Lumia 800, and two contracts at the moment, for my second sim, I need another device, as one number is for work use, the other for social use - and I'm sick of having to change my sims over.

I'm currently paying:
£23.00 for 200mins, 250MB of data and unlimited texts,
£19.25 for 200mins, 250MB of data and unlimited texts.

But between £40-£100 a month because I always use more than my allowance, on both contracts. Even when I upgrade my plans, I'll always use more, and therefore spend more. When I was on a 900min tariff, I'd be paying more and going over more.

My options:
1) Get a new phone contract, paying up to £29/mo but still have an issue, I'd have two device, three sims and three bills - I'd never get to use one number in this case, and still have to change my sims over.
2) Buy a phone outright and use it for my second sim.
3) Buy a budget handset - e.g the from the Nokia Asha range. I like the keypads, but the phone's do look cheap and the screen is a bit, well, yeh.

What I'm asking is, what would you do?

http://www.phones4u.co.uk/htc/windows-phone-8s/ -> The HTC 8S: £21 a month on contract (24months) ,or around £250 outright.

http://www.phones4u.co.uk/shop/shop_contract_details.asp?ItemKey=595642&intcid=prism_Xperia_U_Black -> Sony Xperia U: £10 a month on contract, or around £120 new.

http://www.bing.com/images/search?q=nokia+asha+205&FORM=HDRSC2 -> The Asha 205, probably around £80 new, off contract.

OR: wait 4 months until the Lumia 920/8X drop in price, to justify having three contracts, or buy it outright?