Try ringing tech help. They have always been very forthcoming when I have rung them

Ureka! I've got it.
I received this e mail response from Satmap support,

Main menu>settings>compass settings>grid magnetic angle>”automatic”

Main menu>settings>GPS settings>use GPS compass>”1kph/0.6mph/0.54”

Recalibrate the compass - Main menu>settings>calibrate compass>

I had done the first and last correctly, however in GPS compass settings, I had set it to 3 mph instead of 0.6 mph, as I thought it was to be set to normal average walking pace.
Just set a route to test around the block, and it's bang on now. No fluctuating, steady as a rock.
Interestingly too the blue circle direction pointer has suddenly appeared.
I now think I'm in love with my Satmap.
Thanks for all your help, Les and SC.
Dave.

Slowcoach and Slogger, where are thr boost button and the night setting - sorry hopless with gadgets!

You will find you can adjust the illumination in 'Settings'.
The boost button is the little round one next to the one/off switch.
Dave.

Just a though about your "direction of travel" indicator. This is a feature that was introduced via an update. I wonder if you have the latest version of the software installed. Worth a check.

I just updated my software to the latest v1.5, there is a new feature (for me at least) where you can select the colour/shade of the active route on the map. I can now select a very pale blue so I can see the path detail underneith the active route. If you touch the joystick the route turns to a very dark blue so you can easily view the route overview but normally its quite feint so you can see the detail, this seems to work very well. All selectable in the route/edit option.
Les

Mine came with the v1.5 software, and as ive signed up to the new Expedition planning, I am going to make a few SD route cards. Ive just done one of the Cambrian Way, all nearly 290 miles of it in three sections. Almost 1500 waypoints. The planner and unit can only handle up to 500 waypoints at a time for a route.
I'll do the C2C next, then Offas Dyke.
Dave.

LLoving my Satmap more and more.
I purchased a 4GB SD card solely for use with my Satmap.
Using their Expeditions route planner to great detail with 1:25,000 mapping, I have now plotted and saved onto it, the full Cambrian way, Coast to Coast (official route) and Offas Dyke path.
These are all very close to 1500 waypoints each.
The way they work is - you insert into the Satmap the SD routes card and transfer the chosen route section to 'Internal Storage'.
Then take out the SD card and insert the mapping SD card.
The chosen route then shows on the mapping.
Mine is 1:50,000 at the moment, but obviously will show more details if you have 1:25,000 maps or map tiles.
Dave.

Mine was invaluable today walking between Tailbridge and Brownber Head. No maps to unfold in the rain/sleet/snow. Very poor visibility but easily managed to forge a direct line to the summit by keeping the DOT indicator under a "Go TO" set on the top.

"LLoving my Satmap more and more"

Is it a Welsh Satmap?