Name that series!

[Fuun]

 Hi Everyone. My sister and I are looking for the name of a series that was on TV during the early 80's. It was about an alien species whose secret was only known by a couple of kids. Or at least one, because it starred a girl of about 12 years old. These aliens were disguised as humans, but had no facial expression. I
think they didn't speak either. In their true form they were huge slugs.
When transforming from human into their slug-form, their skin would turn to slime until they were totally transformed into these big crawling piles of snot (with flickering lights inside them). And they made this
slimey sound. 
 
I remember that their lair was an old barn on the country side. And this girl knew where it was. Man I hope there's someone out there that can give me an answer. There must be, given the description I just gave.

Give it your best shot and think hard please! Thanks! 

Koen The Netherlands

[221b]

You could try these websites Koen...

http://www.geocities.com/TelevisionCity/1011/index.html

http://www.80snostalgia.com/classictv/

http://www.tvradiobits.co.uk/eightieszone/

http://www.bigglethwaite.com/uktvqs.htm

http://www.pps-tv.co.uk/

Good Luck!

Helen