Sorry net dropped out so I couldn't edit my post properly:

Firing order still gets me sometimes.

Listen, if there is a knock, you may have spun a bearing. How quickly did you see oil pressure? Did it take a while or did it come up straight away?

I have done a few spun bearings but the most recent one was on a freshly rebuilt engine, and it sounded much different to the previous ones I had experienced.

That is a big jump to diagnose it as a spun bearing, so don;t mean to cause alarm.

Valves should not collide unless you have a fairly serious cam and you have the timing of the cam way out. Hook the exhaust up and have a better listen. Normally the big-end knock disappears as you increase the revs, then arrives once again when you drop the revs, try not to rev too much on the fresh motor though. Might pay off to remove it and have a look, just check everything else first though.