In reply to ScottTalbot:
Mountain Training (and by extension their qualification providers) make a deliberate point of never getting involved in specifically recommending or certifying equipment.
Ropes are certified to EU minimum standards with additional standards published by the UIAA.
However, the vast majority of professional Mountaineering Instructors and Mountain Guides would only consider a single rated rope as being sufficient for professional planned use on graded scrambles in the UK. [For emergency use they might consider a lighter rope only meeting the much less rigorous half rope or twin rope standards.]
Single rated ropes are available in a variety of weights and diameters. In general, the lighter the rope the harder it is to meet the standard, therefore the more expensive it will be. In addition, the UIAA has a "dry" standard for water repellent treatments. It is a demanding standard but ropes meeting it will perform much better in the rain or wet snow conditions but are substantially more expensive. In some cases "UIAA dry" ropes are almost twice the price of untreated ropes. The very thinnest ropes generally come with the dry treatment as standard.
The more expensive ropes tend to offer much better handling. On the other hand, scrambling can be relatively hard on ropes and it is equally easy to completely trash a rope on sharp or rough rock regardless of how expensive it is.
You should be able to buy a basic 10mm single rope for £30-40 which should be adequate for most dry weather scrambling.
Equally, if you want one of the lightest dry treated single ropes available you will probably end up paying £80-£100 for something in the range of 8.5mm to 9.1mm.
Unfortunately, despite all that, it is also very debatable whether 30 metres is actually the 'best' length. Lots of people will argue strongly in favour of something slightly longer (35m or 40m) for more technical scrambles. Equally, I know lots of people who carry less than 30m when it is just for emergency use.
Anyway, hope that helps.