The first British unit to occupy Preetz, north-west of Plön was 6 Guards Armoured Brigade Workshops REME arriving from north-west of Lübeck on 8 May 45, disbanded 14 Jun 45.
4th Armoured Brigade Workshops REME arrived 16 Jun 45 and served there until 10 May 46.
271 Forward Delivery Squadron RAC arrived 16 Jun 45 disbanded 3 Mar 46.
110 Provost Company CMP arrived 1 Jun 45 leaving for Kiel 15 Jun 45, a detachment remained until 29 Jun 46.
81 Special Investigation Section CMP also arrived from Hamburg returning 16 May 46.
Unable to locate a “Scottish Regiment” billeted in the town, however there would have frequent patrols from units based in Landkreis Plön.
Hope this helps
https://britisharmyingermany.com (under construction, now going back starting from 1 May 45)