I can recommend the Discarnect. They are widely available (Amazon, eBay, etc), cheap, easy to fit and work brilliantly. There are naysayers who don't like them but I am very happy with mine.
The previous owner of my TF fitted one of these. He didn't use the car much and said without it, the alarm etc. would run down the battery in 2 weeks. I haven't used it yet, but will be doing soon when I lay up the car. I didn't get round to sorting the crusty bits at the bottom of each wheel arch, so not up for winter driving this year.....