Overpay mortgage or save deposit up?

[Timetothinkagain]

Hoping you wise people can help me!
In a few months dh and I will be in the position to have approx 400 a month we can save/overpay mortgage with (have looked into penalties etc and it's ok to do). Here's my question with added info:
We currently live in a property we paid 90000 for 4 years ago and owe approx 74000. We would like to move in a couple of years to a bigger house. We're working on the basis we need a 10% deposit at least and approx 5000 saved up to cover the rest eg fees, moving costs etc. We hope to buy a property in the region of 160-180 mortgage Etv allowing. Are we better to save money up to get the biggest deposit together we can (to add to whatever we get out of current house when we sell) or overpaying and hoping we get a decent amount for house?
Obviously my concern is that we'd have to accept less for the house and then lose anything we'd save. But then it seems more logical to overpay. I'm not massively savvy financially so would appreciate any input you have. Thanks.

if you overpay your mortgage you are increasing the amount of capital in your current house and thus your deposit for the next one

Yep as TalkinPeace says, it doesn't really matter which you do as if you overpay the mortgage the money will still form the deposit for your next home, it will just be in the form of equity rather than savings.

You could look at the difference in the interest rates- if your mortgage interest is higher than you can get in savings, pay it off the mortgage, if you are on a low interest rate than it probably makes sense to put it in savings. That said I don't think it will make a significant difference either way if you're thinking of doing it relatively soon as the difference in the interest on 4800 pounds (12 x 400) isn't likely to be significant, 48 pounds pa for every 1 per cent difference in interest.