We would recommend using the same timber as the floor if you can. This would make sense and keep your material palette as simple as possible - there are some fantastic timber finishing treatments available that will provide a durable surface that is easy to maintain. There may be a way that you can introduce a separate timber element say 40-60 thick that sits on top of the existing solid top... perhaps a bit like the kitchen in this image by 'Beef Architects'http://www.contemporist.com/2013/06/21/riverpark-apartment-by-beef-architects/ap_210613_07/

Thanks to everyone for all your helpful comments. As much as I'd love the light airy style kitchen with the light grey benchtops, I've decided to go with timber as it will stand up to my boof head hubby, he is just too heavy handed to trust with a laminex benchtop, if he does cause any damage we can just sand and re-oil and will be good as new. I also felt timber on my desktop (area on the side) would be warmer and more welcoming as I work from home and the thought of a cold laminex desktop wasn't appealing. I will try to counteract the over abundance of timber with white splash back tiles and lighter floors when we redo those, hopefully that will lighten it all up a bit. The buffet in the dining is going and will be replaced with something in a lighter tone so that will cut down on the timber as well and the stools will be painted to match the cabinets. I'll more than likely do away with all the timber furniture and go lighter soon anyway....a change is as good as a holiday they say, and I can't afford a holiday now I've got a new kitchen so..... I'll post photos of the finished product but thanks for all your help.

I think it is good to mix up the warm and cool colours. We have warm furniture too so its just the walls that are cool. I even have a beige/stone coloured curtain next to the grey wall and it looks so nice. Because this is an open plan room do you think those type of tiles will be too busy? I always go for plain things but i can see how something like that would look really good! This is one big room with lounge, dining, kitchen and french doors that open to a massive decking. I will post a pic of the whole thing when the final benchtop and tiles go on

Use a strip off the front of the existing benchtop to become the front of the new benchtop with a join. Use two new benchtops to fill in bench around the new sink. With a joining seam at the back behind the sink, unnoticeable. The existing benchtop may need to be sanded and revealed to gain a uniform colour. Fiddly but it is the same principle as used on a stone benchtop to make it look substantial when in fact it is not. Best of luck