Dublin to Bristol, UK via air

If you're asking about the Bristol, England (not Wales) airport, it's small and simple (four or five gates, the terminal is only a couple of hundred feet long, and the bus area is right outside). The only nearby rail station that I know of is about five miles northwest. It's (Something) - Blackwell. If the question is only can you make it to the bus area: sure - - if the flight's on time. If the question is can you make it to some train station: beats me.

Thanks for correcting my mistake Ed. I am speaking of Bristol, England. The First Great Western bus from the Bristol Airport delivers us to the Temple Meads Rail Station. So my question remains:
Is 55 minutes sufficient time to clear immigration/customs at this airport and still board the bus?

Yes.

Well, it should be enough time, but you are making a journey with several different connections, and at any one of them you could experience a delay. That will only really matter if you are booking a particular train in advance. Although there are trains every hour from Bristol to Penzance (usually with one change en route), reduced price tickets bought in advance will only be valid on one particular train. If you miss that, you will have to buy another ticket at a much higher price. Buses from the airport to Bristol Temple Meads station run every 10 minutes and should take 22 minutes for the journey. How much time are you allowing between arriving at Temple Meads and actually getting on the train? It is a large station, so 15 minutes would probably be comfortable. My advice would be that you either time it fine, but buy an "open" train ticket which can be used on any train, or make greater allowance for possible delays and buy a cheaper ticket in advance which will only be valid on a later train. Buying tickets in advance would also give you the security of having a booked seat. Some of those trains can be very busy.

Good tips Bob. Looking at buying tickets through online site: thetrainline.com Trip departs airport @ 8:30, arrives Temple Meads @ 9:02; Train departs 9:13 and arrives in Penzance @ 13:17 Train is specified train only, no refunds and passes through Bridgwater. So I will look to for an earlier bus leaving the airport and build at least 15 minutes to board train. Would you recommend a different site to locate tickets?
First Great Western is the train company.

Delays are likely to be caused by the late arrival of the plane at Bristol, delays in processing or waiting for bags at Bristol Airport, and traffic holdups on the way to Temple Meads. They are all unpredictable, and you have to decide on your own comfort level. There is no need to book the Airport Flyer, and you should just get on the next bus that arrives. There is no point hanging around at the airport. I have not flown into Bristol from Ireland, so am unsure what formalities there are. As U.S. passport holders, you may have to complete landing cards. Baggage usually comes through fairly quickly. Are you intending to collect tickets at Temple Meads, or are they being sent to you? If collecting them you need to allow time, and there may be queues at the machines. It is a busy time of day. It doesn't make much difference who you buy the tickets from, but some companies charge a booking fee and have different requirements for non-U.K. credit cards. If the Trainline process gets difficult, it my be worth trying First Great Western or Cross Country. If you are worried about missing your train, there is a later one at 09.44, but it takes longer (there is a change at Plymouth). If I am being cautious, it is because i don't want you to blame me if things go wrong!

Firstly as you are arriving from Ireland there won't be any customs or immigration to be concerned about - although I would guess you would have checked bags to collect. My own experience with the only time I used this bus was not I have to say good at all. It arrived 15 minutes late, took over 10 minutes to get everyone board, (leaving some behind) and then took nearly an hour to Bristol - and this was on a Saturday afternoon. I may well have been extra unlucky but I would therefore urge rather more margin in your plans.

The traffic in the Bristol area is notoriously unpredictable. Precise time of day, school terms vs school holidays, home football fixtures, especially an important match, and bad weather can all make a big difference. Worst of all, any incident on the M4 or M5 motorways to the north and west of the city can cause gridlock over a wide area. Deb may have a very easy journey in from the airport, or it could all go wrong. Her decision to go for an open railway ticket, combined perhaps with a seat reservation on the train she hopes to get, is probably the best one.