The British Geological Survey (BGS) has published a report on the shales of the Midland Valley of Scotland with estimates the total resources of shale gas and shale oil in place. They estimate the oil resources to be between 421 and 1497 million tonnes and gas to be between 1.4 and 3.81 trillion cubic metres. You can read the report and a short summary here:

https://www.gov.uk/government/publications/bgs-midland-valley-of-scotland-shale-reports
The BGS emphasises that these figures refer to an estimate for the entire volumes of hydrocarbons contained in the rock formation not how much can be recovered. They also point to the complexity of the Midland Valley geology where shale rocks are mixed with volcanic rocks, faults and abandoned deep coal mine workings which make it more complex and are likely to limit where wells can be drilled.

The estimated resource is much smaller than that estimated for the north of England where the BGS estimated there may be some 40 trillion cubic metres of shale gas in the ground.

The UK Onshore Operators Group welcomed the findings but the World Wide Fund for Nature argued that the reserves should be left in the ground. You can find a summary of reactions in an article in the Guardian: http://www.theguardian.com/environment/2014/jun/30/scotland-shale-gas-reserves-a-fraction-of-northern-englands