Any of you techy`s out there can answer this please.
If a garage changes any settings within the ecu does it leave a date and time stamp

You'll need to be a bit more specific! There are many ECU/Modules in the vehicle.
Do you mean changes to the CCF (Car Configuration File) or updated firmware to a
Module?
CCF keeps the last date an alteration was made. MY15
Tyre Pressure Monitoring System (TPMS)
Surround Camera System
InControl Apps soon to be replaced with CarPlay (WIP)
Meridian Premium Surround Sound
Digital Audio Broadcast
Timed Climate
Cruise ECO Data
Follow Me Home Reverse
Extra Features Menu
Picture In Motion
4x4i screen (WIP)
Digital Broadcast TV
Meridian Rear Media with WIFI
Factory Powered Tailgate
Blind Spot Monitoring (BSM)
Reverse Cross Traffic Alert (RCTA)
Electrochromatic Wing Mirrors (WIP)

must e the ccf. I have a suspicion that the car was remapped in the past and wondered if there was a way to check

Remap doesn't get logged as a CCF edit.
Very unlikely you will be able to find out as the level of expertise in finding this would be well out of the skill set of your brightest LR service tech, possibly a high ranking LR engineer. MY15
Tyre Pressure Monitoring System (TPMS)
Surround Camera System
InControl Apps soon to be replaced with CarPlay (WIP)
Meridian Premium Surround Sound
Digital Audio Broadcast
Timed Climate
Cruise ECO Data
Follow Me Home Reverse
Extra Features Menu
Picture In Motion
4x4i screen (WIP)
Digital Broadcast TV
Meridian Rear Media with WIFI
Factory Powered Tailgate
Blind Spot Monitoring (BSM)
Reverse Cross Traffic Alert (RCTA)
Electrochromatic Wing Mirrors (WIP)

ok many thanks. didn't want to drop myself in it with insurance.
just my mate reconds it pulls better than his with the same caravan on.

ECU should still have a programming date internally, but the only way to tell if it has been mapped is to read the file

Don't know if it is applied to the FL2 as well but on the bikes i had i simply downloaded the ignition and injection map from the bike and done a simple windiff comparison with original map forum members gave me.