I think Saturday's run has given me confidence at last.
Managed ot get to bed in time to get up and run this morning - there were stars in the sky at 5.15!!
Walked for about 3/4 mile then began to jog - felt ok but HRM was beeping - so instead of walking I turned it off!
And ran, pausing for stretch at a suitable bus shelter and then ran most of the way round the (undulating) route - 4.5 miles done, 30s / mile quicker than last time for the same route and AHR 8 higher. The three running miles were at the pace I need to run Amsterdam to avoid the cut-off :>)