Get some feedback on your site or ad from other rental owners and techies. Also a library of online resources so you can make DIY improvements to your web presence.
I don't believe you should have an issue with dupicate content in meta descriptions. Firstly, your meta descriptions should be in the local language for the local language pages, and secondly, each should be unique wherever possible and optimised for that specific page. I know it sounds like a hassle, but ultimately worthwhile in terms of traffic.
More generically, we're you just to have one local language description across all local language pages, Search engines aren't looking for duplicate meta content, they penalise duplicate CONTENT (as there are software programmes which crawl the web, stealing content, and auto-creating web pages with google adsense advertising on them to make money for the publisher).
Have you tried checking the search volumes on your target phrases "villa in crete" and "accommodation in crete"? Wordtracker is a good place to check - you can also use the Keyword Tool in AdWords for a different perspective.
It's important to know whether people are out there looking for these - then you know it's worth chasing them!
Don't worry about losing out by changing to targeting some different keywords. I lot of the work you'll need to do is on the links that come to your site, rather than the site itself.
Regarding search volumes for target terms, I initially did this (used a free program called webceo), have just redone and got completely different results. Tried wordtraker and then redid with web ceo got similar results on the day but very different to initial results months ago. I suppose with holiday search terms they would be specific to seasonal variation. Is there any way to get an annual average or search specific search term volumes by month.