Anything less than £6k and you're ok.
Anything over £16k and you're entitled to no means-tested benefits.
I would assume that your entitlement changes, as soon as your financial circumstances change, so if I was you, I'd try and reduce your savings to £6k as soon as possible.
Take a look here:
http://www.entitledto.co.uk/help/savings.aspx
Copied from the above website:
"If you deprive yourself of capital in order to increase the amount of benefit you get you can be treated as if you still had that capital (this is called ‘notional capital’). This might occur if you give money away to members of your family or buy expensive items in order to reduce your capital.
You will not be considered to have deprived yourself of capital if you have paid off debts or used money on ‘reasonable’ spending on goods and services."