What would you do? Ex-EU flight times

Flying EX-DUB the night before our VS flight. Flight departs DUB at 20:40 on BA839.

Trying to work out which positioning flight to book - would you go for:

(a) the BA838 which gets into DUB at 20:05 and should presumably be the plane that will return to LHR on the BA839 at 20:40 (benefit is that if the 838 is delayed then 839 should be too ... but might be tight if long passport queues at DUB and would be near impossible if they decided to change to another plane for the 839)

OR

(b) an earlier Aer Lingus flight - benefit is that we should get to DUB earlier, but risk is that it could be delayed and we'd then miss the BA flight. Would also be less convenient as we'd need to leave LHR earlier and leave work earlier.

Thanks for any advice!

Personally I'd go early enough to have a nice bit of lunch and a wander around Dublin , why make it tight and stress out

In theory the BA838/839 back to back combo is safe as houses - DUB passport control & security should be pretty quiet that time of night.

I wouldn't do the 838/839 combo - you could assume BA will use the same metal for both flights, but of course you don't know their operations schedule, so what if they don't? What if the 839 is operated with metal that arrived in DUB earlier? You've then got a very tight connection, and if the 838 is delayed your stuffed.

Take an earlier flight and don't risk it. Even with Aer Lingus make sure you allow for approx 1 hr delay if you can - apparently they're often delayed, and I got caught out last year with a tight connection due to delay with what I thought was a good allowance. I made it, but it was a bit stressful and I could do without it. The plan for the next ex-DUB is to make sure there's plenty of time.

When I took the BA839 in September, I booked the earliest positioning flight I could to make it into a day trip to Dublin. Personally I'm too scared to to the back to back thing, as although the risk is low, it would be a lot to lose if the first ex-dub sector was missed.

It is the basic only real fail point of the trip, once you get onto the first leg of the ex-EU, then its up to BA to sort out if there are cancellations and changes to schedule.

But if you don't make it, all bets are off and you've lost the trip. Not even sure what travel insurance would give for that.

Personally I always give a 3 to 3.5 hour connection time at Dublin, but coming in from Birmingham. I've had doubts as to whether that is enough though.

But once you are there you can relax and be assured you'll start the trip...

Before I took my trip, I had a look over the terms and conditions of my (pretty robust) travel insurance. I was rather concerned that it would likely not be covered, since the policy (and in my experience, many other insurance policies) only included trips starting from the UK within their scope. I would be interested in others' thoughts on this.

Thanks for all the advice, everyone!

Really keen on the idea of an early flight over and enjoying a day-trip in Dublin. Only problem is that my partner and I have pretty much exhausted our holiday allowance and whilst we could get away with leaving the office at 3 or 4pm taking the day off might not be viable. But I see the risk and having a stressful start to our big summer holiday is the last thing we want, so perhaps we'll just have to do it. Decisions, decisions!

The BA Flyer-Talk forum rates a back to back at Dublin as "Good" (can go up to excellent)
Have a look here