Solved my earlier problem of wanting COG, SOG and depth in bright big letters on a screen without using up chart plotter real estate:
Lowrance M 52 i £219 - no map, GPS, depth 4" b/w
Lowrance M 56 i £269 - outline map, GPS, depth 4" b/w
Lowrance M 68 i £409 - outline map, GPS, depth 3.5" daylight colour
Have chosen M68i married to 7000C plotter for a total of £1738 incl VAT, delivery, compared to the more obvious solution of the combo LX 104 C which costs a £2299, or an extra third on the budget!
I lack in my solution the more powerful sonar and the ability to display a high resoltion map of the sea bed and the fishes..... but since it is to be a glorified depth finder (number only) and navigation 'repeater', this seems the best solution. And I can look at the pretty picture of the fishes on the colour screen if I am bored when my wife is driving....