There seems to be a small flaw in your plan, Boxtops. According to the Gatwick Airport website there are no direct flights to Munster:
http://www.gatwickair...flights/destinations/
The Munster Airport website also only shows flights from Stansted:
http://www.flughafen-...becc7d48ef64d1f851e39
Bremen Airport is marginally closer to Diepholz than Munster is but, again, flights are from Stansted, not from Gatwick:
http://www.airport-bremen.de/en/flights/
I don't have much faith in your local travel agent either, Greenrook, because there are no flights from Newquay to Newcastle!
Looking at the list of services from Newquay (and remembering that Air SouthWest are pulling out of Newquay after this week)
http://www.newquaycor...x.cfm?articleid=48607
and combining it with the information on the Bremen & Munster websites suggests considering Newquay to Edinburgh (with FlyBe) and Edinburgh to Bremen (with Ryanair). However I've not checked that those flights will be operating early next year ( - services from Newquay are often seasonal - ), neither have I considered any connections.
Annoyingly, the Newquay airport website shows a blank page for 'Winter Services' but Wikipedia indicates that the weekly Lufthansa flights to Düsseldorf don't operates during the winter months (and they're not currently listed on the Düsseldorf Airport website) so a direct flight to Germany seems to be ruled out.
So I'm sticking with Newquay > Edinburgh > Bremen
Bremen Airport is only 3km from Bremen rail station, with a frequent, direct tram service. From there you've got an hourly direct train service, taking just 41 minutes to Diepholz.
Chris