Good morning Mark,
In The Netherlands there are two types of grounds; owned by a association (the members own the ground) and commercially grounds (run by a company or private owner).
For the first type you often have to be (or become) a member, openinghours are limited and the accommodation is often simple, but normally it is cheap because they don't have to make a lot of profit.. If you are not a member there is most of the time a possibility to use the facility but you have to get in touch with the association first.
The commercially run grounds are run as businesses. You can use the facilities they offer like: gun hire, instruction, restaurant etc. I think this is like the same in the UK.
Then your question: If you are staying in Middelburg there are not to much possibilities. In the near there are 3 shooting grounds: 'SV de Schutterij Clinge', 'Schietcentrum 'Reymerswael Rilland and 't Trapke op, Huijbergen'. The first and the last are association grounds, 'Schietcentrum Reymerswael' is out of order.
To get to commercially ground you have to travel. Near Rotterdam there is 'Schietcentrum Europoort' (1 hour drive), In Weert there is 'De Wildenberg' (two hour drive), near Tiel there is 'KSV de Betuwe' (1 hour, 40 min) and near Oss there is 'Schietbaan Eric Swinkels' (1 hour, 40 min drive). All beautifull grounds with very good facilties. For Information check the websites:
SV De Schutterij Clinge:
http://www.svdeschutterij.nl
Schietcentrum Europoort:
http://www.schietbaan.com
De Wildenberg, Weert:
http://www.schietbaandewildenberg.nl
KSV De Betuwe:
http://www.ksv-debetuwe.nl
Schietbaan Eric Swinkels:
http://www.kleiduiven.com
If you have any more questions, please let me know,
Best regards,
Pieter