It was speedway in the 1950's, initially for training but the Ringwood Turfs were members of the SAL in 1954/5. It was later used by Poole for training in the early 70's.
The track you saw racing on was the 'mini longtrack' which was closed after a sidecar fatality in 1992.
Ringwood Side by side georeferenced maps viewer - Map images - National Library of Scotland (nls.uk)
Exeter Side by side georeferenced maps viewer - Map images - National Library of Scotland (nls.uk)
Interesting to see that Exeter was an athletics stadium pre-speedway.
Report and results (written by a Yank I think due to use of "gotten" and "besting")
Cossar Stars In Sidecar Triumph — Official Belle Vue Speedway (bellevue-speedway.com)
I've been to countless grasstracks, the first in 1972. I even competed in a few on my JAP in the 90's. Despite this, I never did and still don't get excited by the sidecars.
I agree.
I struggle to see who they appeal to. I see them more as light cars than motorbikes but my car racing fan mates think the opposite hence they fall between 2 stools.