Update, (but not a good one) Couldn't do any work today as let down by suppliers, so thought Id have a play as the weather was good, cleaned the filter from the bottom of oil tank, new oil filter fitted, and filled with 7 L of Shell's finest (as a start), NO CHANGE
connected hose to breather from top of oil tank to avoid covering front of engine with oil again, and to start all appeared ok, even when I gave it some gas no sign of oil from the breather, exhaust was smoking a bit, but I hoped this might be residual oil being burnt off (fat chance), but as soon as temp climbed up then oil started coming out of the breather when engine revved
So to summarise the symptoms are :- blue smoke from the exhaust, oil being forced out of the oil tank breather when temp is up, and engine revved, f***ed if I know