Most of the UK mainland is actually not very far from one form of fibre optic cable or not, the problem is usually that final couple of miles link between the premises and these existing cables, and there being a suitable wholesale arrangement to allow retailers to provide a service. In Shetland, the new fibre optic cable between Maywick and Lerwick is due to go live in a few weeks, with the ability then for local telecoms firms to use this fibre as the backhaul link between areas.
The Shetland Times has a nice simple map of The Shetland Cloud which reflects where fibre optic cable is available along with a lot of other information on the broadband situation in the area. While there are larger BDUK type projects underway in the Highlands and Islands, the timescale of these does mean that a community led scheme to take a fed from this network and install their own fibre or wireless access points might be a preferable solution.
It should be pointed out that while the BT ADSL2+ upgrades mentioned in the article will improve speeds, it is fair to say if you only connect at something like 4 Mbps (phone line length of around 4km) or slower now then the improvement in downstream speed will be minimal. Those that will benefit most are those who already getting 6.5 Mbps or faster (generally lines shorter than 3km).