A quick update: Whilst carrying out important normal non-IT work (!) having Christmas Celebrations etc we've managed to finish a modified crisp white skin evolution version store and this is now live. We also have a nice and tidy, fully functional standard skin / custom module powered, evolution version in reserve just in case
The live store uses modified crisp white skin / our own custom module / an XC provided bug patch (until 5.3.2.3) / our own core patches and quite a lot of 'temporary' custom CSS, but still happy with the result. We wanted the evo-cws based site to be live from 1/1/17, so we're just in time. Later next week, we'll attempt to finish the alternative (evolution) version of our custom module (on a dev store first) as discussed previously. This should negate those patches and massively reduce the quantity of Custom CSS as part of the end result. Happy New Year!