Corsa won't start. ECU problem?

A replacement engine was fitted, by my Granddad, to my Corsa 1.4, sri 16 valve (Kreg 2000), as previous engine 'big ends' had broke.

Was collected after completion (car has been off the road for 7 months by this time) and started first time.(Revs were stuck at 10000 rpm on idling but thought this was just needing adjustment.)

Drove 5 miles and stopped for meal. Started up ok after 30 mins break but after 1 mile engine lost power and eventually stopped and refused to start up again. Dashboard lights were on but car would not even turn over.

Only warning light showing is Yellow (engine block) light but this showed when car originally broke down.

Strangely enough the symptoms of this breakdown were exactly similar to original breakdown symptoms!

No other ECU lights or codes showing.

Also we later found out that although the engine supplier had verified that the engine was a 1.4 Sri I have been told by my Granddad that it is a 1.6!!

What would you think the problem is?