You shouldn't have to get a special insurance for a few months. In theory, with most insurances within the EU, it is only on renewal, with an address in another country, that you should have to get a local insurance.
Is it specified in writing in your contract? Maybe you can get quotes for other UK insurances for more than 1 month abroad...

 

Browsing a bit on the Internet, I found some information on car insurance covering more than 30 days abroad (EU countries):

Aviva: European cover - 180 days per year as standard, up to 90 days per trip
Budget: car insurance policies provides EU cover for up to 60 days - normally can be extended by calling the company.
Endsleigh: includes cover in EU for up to 90 days.
John Lewis: long term cover (up to 90 days in a policy year), and offer extended cover automatically. They also offer options for long term European breakdown cover.
Saga Car Insurance: Unlimited ? Be careful here as they sometime offer a different policy badged Saga Select via a broker panel. If this is the case check carefully the European cover being provided as it may differ from the standard offer.

I also found another list here.

In theory many of the car insurance provider offer extensions that can cover you for longer periods (several months).