Dual IP and landline telephone

[#1]

I am on a Broadband/Home Phone bundle with PlusNet and intend to utilise the free evening and weekend calls as well as using VoIP telephony to speak to my brother in Germany. Therefore I would like a telephone which I can have as both an IP phone and a landline phone. I am using a laptop and don't 'station' it in my flat, instead using it at several points around the apartment. So...
Is there a 'wireless' VoIP phone which I can plug into the landline and not necessarily the USB on the computer?
Which dual landline/VoIP telephone is the best/would you recommend - for clarity and value?
Many thanks.

[#2]

HI,
I've just purchased a dual phone which I have plugged into my router and telephone socket and it works great with my normal dect phone system.  Depending on how much money you wish to spend, there are several you can choose from. I was looking at the Siemens Gigaset range as they are cordless dect phones, so you are not governed by wires and you can switch between making normal calls and voip calls. I believe that the only ones available in the UK at the moment are the Gigaset S450IP, S675IP and just recently available the C475IP. 
Tesco's do the S450IP but sell it under a different model Tesco Siemens DP450 dualphone.  Don't make the same mistake as me in thinking that this phone, although locked to Tesco, would still retain all the functions of the gigaset S450IP, as tesco has disabled the ability to register 6 voip accounts and access to gigaset.net. So in effect you can only register with Tesco.  If I hadn't managed to get mine half price, I think I would have purchased the original gigaset S450IP and not the tesco one as at full price there isn't much difference if you shop around on the internet.