Thank you for all your replies. I will look at all your suggestions and then we.
We do fly in J long haul (Y is a no-go due to my husband's height & long legs) and as we do a lot of shopping while we're there, we appreciate the bigger baggage allowance which BA would give us.
We thought about Aer Lingus over to Dublin from Newcastle, but would need to pay for extra baggage so we though of using avios to cover the Newcastle to Dublin flights in Club Europe.
Most of the flights offered by BA involve flying into Gatwick and out of Heathrow which we are loathe to do.
We chose AA for our return flights to Dublin as we used them last year and prefer their seating to BA.
TBH I added in an overnight at Dublin on the outbound journey and car hire for the month and it is still costing less than the J flights alone which we did in October. We will also need to add on an extra bag or two for the DUB to NCL flights as the Club Europe tickets only allow 2 bags rather than 3. I though that you got an extra bag when you turned silver but I was wrong. Still it's only £40 each bag so that's fair enough.
Katie