FREDA I'm sure you can google, but it is a mnemonic used for periodic checks when enroute.
Stands for
- Fuel
- Radio
- Engine (including Carb Heat)
- Direction Indicator
- Altitude
Re D&D - that is an old document.
This one is newer:
http://airspacesafety.com/wp-content...n_shawbury.pdf
Essentially - coverage will be pretty good above 3000 feet UK wide, although in practice will be better than that. Note that London Centre now cover all of the UK, with directional finding stations now also covering Scotland. If you have a genuine emergency - evidence shows an airliner is likely to pick up your transmission.