Remote GPS sensor?

From experience with an elderly TomTom One I would very much like an upgrade/replacement which I could mount where its GPS reception would be poor, eg up under the metal roof of the car. Presumably units supplied ready fitted in some cars would have this problem. Is there a Sat Nav model on the market in the UK which would have the option of a remote GPS sensor?

Loads of the older in car sat navs have the option for external antennas using the tmc connection