Scottish info is precisely that, information service, and IMO you will not require the filing of a flight plan, unless it goes IFR, in which case, you would follow the IFR arrival procedure, as per your filed IFR flight plan. IFR only for Islay and Benbecula, Oban does not have a published procedure. You would want to do the flight VFR though, for a good number of reasons.
Purely out of interest as to the options of howthis flight could be flown if it did turn IMC, is there any benefit/requirement to file an IFR plan which would involve getting up in the airways, as most of this area is uncontrolled airspace is it legal to stay lower (and hopefully below the freezing level) and just pick up a basic service while flying IFR then fly the prodcedure upon arrival assuming an out of hours /non towered field with a published approach ?
Edit to add: or if the tower is manned at arrival time, pick up an approach clearance for landing when nearing the field ?