The System76 Gazelle Pro sounds like what you want:
Edit: comes with Ubuntu preinstalled, so hardware support should be fine.Code:4th Generation Intel Core i7 CPU's 15.6" 1080p Full High Definition LED Backlit Display - Glossy or IPS with Matte Finish (1920 x 1080) Intel HD Graphics 4600 Up to 16 GB 204 pin Dual Channel DDR3 @ 1600 MHz 1 x mSATA, 2 x 2.5" 9mm Removable SATA II/III Multitouch with two finger scrolling Gigabit LAN (10/100/1000), WiFi Intel Centrino HDMI, VGA, Ethernet, eSata/USB 3.0 Combo, 2 x USB 3.0, 1 x USB 2.0, Headphone Jack, Microphone Jack, SD Reader Built-In 2.0 MP High Definition Webcam Kensington® Lock Suspend and Resume Removable 62.16 Wh 6 Cell Smart Lithium-Ion Full Range AC-in 100~240V, 50~60Hz, 90W AC Adapter, DC output 19V, 4.74A 14.72" x 9.92" x 0.55"~1.24" (WxDxH) 5.40 lbs. (2.45 kg.)
Thanks to everyone for your responses!
The Vivobook I won't consider, like the Dell FHD ultrabooks, for having a 13" screen. I realise I can plug these machines into an external HDMI display but that won't always be available as an option so I want a decent sized (15"+) internal display.
MSI GX60, at least the model I found that had ATi, suffered from having an A4 CPU.
I have been unable to find any real laptop customization options on HP's UK website. If you know where such a page is then please link it!
I was aware of System76 but didn't consider them as I didn't think they shipped to the UK but thats no longer the case it seems although I don't know how much I'll be paying to have it flown over the pond yet. Provided they don't charge silly money for the postage, the Gazelle Pro upgraded to 8GB and an i7 would seem my best bet. Not only does it work out cheaper than the Vaio E17, it has the plus points of not forcing me to pay for a copy of Windows I'll never use and I've never forgiven Sony for stealing Linux from PS3 users and selling that console under false pretenses (Look! Its a computer too! <sneaky firmware update> Now its not - haha!).
As for FLOSS Radeon status, is this the best page?
I don't know if i am too late to answer you but I use Samsung Ativ Book 8 with Intel Core i5-3230M processormAMD Radeon HD 8850M, 8 GB RAM, FULLHD screen. It works great with ubuntu 12.04 so it should be good.
Sammys Activebooks are extremely nice, 'tho a bit expensive. Most likely I'll get one with I7 and 8870 HD. Two main problems with recent Sammys are unstable WiFi (this one is more related to Intel WiFi card than Samsung) and not so positive approach to Linux installed on their systems.
For something reasonably priced with hi-res screen and i7 i'd recommend Dell Vostro 3560. It has nice features, reasonable price, good warranty terms (it's business line after all) and Dell doesn't mind selling it with other OSes (Ubuntu, RHEL) so no MS tax.
The Ativ book 8 looks like it would be a good choice for someone who wants a top end AMD GPU and is willing to pay extra for it but thats not me. I'd prefer the i4600 graphics of the Gazelle Pro, mainly because it will be cooler and quieter but also because I've had the best experience with Intel out of all the open source drivers.
The 3560 only seems to be available with Win 7 or 8 in the UK and it is said to have a 'HD' screen which usually means 1366x768 which, like most Phoronix readers it seems, I believe to be a sick joke of a spec in 2013. It deserves to have died an unceremonious death a decade or so ago. I was originally only specifying 1600x900 (HD+) and up but now I think I have to insist on FullHD and 15"+ as minimum display specs so that my phones display doesn't take the piss out of my new laptop.