(National Library of Wales home movie, 1958)

Viewable on the BFI Player. It's unclear whether these views are from before the coaches set off or after. Noted are these:
Theo Roberts of Cefn Mawr operated GCA15, a 1949 Dennis Lancet with Yeates body:

Ron Hughes advises 447GRE (Bedford SB/Duple Vega) was with Butter of Childs Ercall, Shropshire when filmed. It was new to Greatrex of Stafford in 1955. It's alongside 314CTE, a 1957 Bedford SB3/Duple Vega operating for Kynaston of Newton-le-Willows:

Next to 314CTE is Price of Southsea (Wrexham) GUN54, a 1950 Bedford OB/Duple, and behind 447GRE is Crosville KW251, a 1951 Bristol LWL6B with full-fronted Eastern Coachworks body:

Seen twice is Voel Coaches of Dyserth MDM562, a 1955 Bedford SBG/Yeates Riviera III, although I can't identify the gentleman standing in front: