What on Earth are Glis Glis?

It's always interesting when you hear of a british animal that you have not heard of before.  But talking to Dave Kirby of Old Bill's Pest Control the Glis Glis could spell trouble for areas like Uxbridge.

Glis Glis are small rodents, similar but a little smaller than the grey squirrel.  They are also known as edible dormouse.  They get into lofts and make a racket above householders, scratching around a lot and they are also destructive with their rodent chewing.  They hibernate for 7 months a year.

Glis glis were re-introduced to the country in 1902 by Baron Rothschild who brought 6 into the country.  A semi-protected species they have to be removed by licensed controllers.  They are localised to the Tring area, but they have been found in Northwood and Rickmansworth. I wonder whether they will spread further?