Mortgage Target

Hi folks, Can anyone answer the following query? In a years time I hope to upgrade to a larger house (I am currently a first time buyer). I hope to find out what monthly net salary I should aim for (or do lenders look at gross?).? My situation is described below-:

Current House:

2 bed terraced (not ex council) Cost 86k Mort 81k Bought 31/07/2005

Target House:

4 bed detached Cost: 200k (+- 20k) Deposit: 10% (+- 5%) Buying: End of 2007

Never missed a mortgage payment, had some defaults 5 years ago, but clean since then.

Me and my partner buying, she doesn't work I am full time Software developer.

What would you say my options are?

Thanks