Luckily, I only had 19 litres, as I was engrossed in watching the syphon tube to ensure no rubbish got sucked through, that I did not keep an eye on the level going into the keg. As I stopped the syphoning, I noticed the keg was just about full. If I had 22 or 23 litres , I would have had some spillage. Lesson one learned.
The other issue I had was my first attempt at force carbonation. what I didn't do was to burp the keg before a gave it a shake when under CO2 pressure

I force carbed at 30psi at room temperature, shook the keg several times then popped the keg in a Fridge at 12C.
Yesterday, two days after carbing, I released the pressure from the keg, set the regulator to 10 (ish) psi and with a party tap connected to the keg via 6 feet of 3/16 line poured my first beer. It was good, not too much foam and a very tasty beer


I think more by luck than judgement I got a great beer served pretty well, I guess the error on not burping will probably reduce the life expectancy of this brew, so it'll need drinking reasonable quickly - no shame there.
Anyway, two more used kegs have been ordered from the Malt Miller, I will have a Son of Punk IPA to keg this weekend and also permission granted to look into a kegorator/keezer build

Apart from the newbie errors I was very pleased, most of the information was gleaned from posts on here, so many thanks to the those who helped me without knowing it.