OK - after going ballistic at the details on that web page, I have had a word with the CAA.
The web site is very badly worded, but will be changed I am now sure!
Basically, although Cumbernauld and Strathaven are technically inside R503, there are local exemptions being drawn up which will allow people to fly in and out of these sites without talking to anyone other than the airfield operator. No transponder needed either.
In the case of Strathaven, the route in will be from the south, in the case of Cumbernauld, it will probably be from the north east.
In the case of Strathaven you will even be able to fly non-radio, as usual.
However, YOU WILL NEED PPR.
The airfield operators have to inform Glasgow ATC a hour before operations (not "first take-off" as the web says), so if you camp the night at Oban, and want to get back to Strathaven by 8am so you can go to work, you must let Strathaven know so we can "activate" the airfield.
The big problem will be if you want to do - basically - a zone transit.
Then you will have lots of info to give. Personally, the Strathaven flying school won't be going in to R503 - other than the 2nm radius "exempted area" around us, which technically is "in" R503.
If we are going to Cumbernauld, we'll just depart to the south, head past the M74, turn up to pass east of Harthill and then enter EGPG's "gate".
Now, all we need is some weather!