Good luck Paul !  Run hard, but smart -- don't get pace focused in those first 5KM, let the pace come to you during the meat of the middle 15K, then bear down the for last 5K.  You know it will get hard; there will be dark times, but trust your training to deliver the result.

thanks milktruck, went so well. Sub 8min miles upto 9 miles then tagged a faster runner who came past me (staggered starts on a trail). He pulled me a long at 7:15 to 12 and I managed a faster last mile on my own. Missed 1:40 by 7 seconds! But very very happy - and sore

That's great Paul! Much much better than your 1:45 goal! You must be very happy, and rightfully so. Congratulations!

thank you both. Now I have huge half marathon experience (all two of them) I will try and give an opinion on peoples queries where relevant (or not)

very true - looking at your logs though you have plenty of experience (and miles) in those legs of yours!