I apologise for not providing more details in my original post and thank you all for your really helpful and insightful posts.
I planned to travel from Belfast to London by Dublin but on arriving at Dublin port we were informed that due to bad weather the ferry would not be traveling that night and that due to expected adverse weather there wasn't likely to be ferry service for two days. Irish Ferries then and there refused to help as they argued that our contract was with Virgin Trains and that in their own terms and conditions if there's adverse weather they supposedly don't have any responsibility to help you.
We then called Virgin Trains and after a lot of waiting (we were roaming so very expensive waiting) we got through to someone who said that if we did not complete the journey that day we'd have to buy new tickets. I had suggested to them we could complete the journey by taking the ferry from Belfast to Scotland that was due to go early the next morning but they argued that nope despite the ferry issues in Dublin we would have to buy new tickets if we wanted to do that.
So knowing we could no longer continue the journey we at huge expense flew from Dublin to London.
If it is of interest here are some brief bits of the replies from Irish ferries, Virgin Trains and my bank.
Irish Ferries:
" We are compliant with EU passenger regulation 1177/2010 which defines the rights of passengers to compensation/refunds in certain circumstances. Because the cancellation was due to adverse weather conditions you are not due any refund of fare ( article 14 of the regulations) however you should contact Virgin Trains for a refund as they were the retailer for the journey. "
Virgin Trains:
"I understand your frustration following your severely delayed Sail Rail journey. However, I feel I must reiterate my colleague's advice that, although you have purchased your tickets through Virgin Trains, any compensation due for this delay is the responsibility of the service operator who you have booked to travel with on the affected leg of your journey. In this instance, as your pre-book Irish Ferries service was cancelled, your claim for compensation should be submitted to Irish Ferries for their team to consider. I am pleased to note that my colleague has already forwarded the details of your complaint directly onto Irish Ferries and so trust that you will hear from them in regards to this shortly."
My bank:
"Thanks again for your time on the phone earlier today.
As discussed, I have contacted both Irish Ferries and Virgin Trains on your behalf. When I spoke with Irish Ferries, they advised me that in a situation like yours the correct procedure is for the customer (yourself) to contact the retailer (Virgin Trains) who sold the ticket or tickets. I advised them that you had already done so previously but had not received a response, however Irish Ferries confirmed that, again, this must be chased up with the retailer directly.
I then called Virgin Trains about this but was told they were unable to discuss the matter with me for data protection purposes. Whilst on the phone to them I did ask, hypothetically, what the procedure a customer should follow if they had already been in touch about a complaint and had been told by Virgin Trains that this had been passed on to Irish Ferries but the customer had still not heard anything. I was advised to give you the following number for Virgin Trains to contact about your concerns: 03331 031 031 (select option 1, then option 4, then option 3).
I am sorry we have not been able to help you any more with this matter and would like to advise you that I will now send you my final response letter explaining a bit more about my investigation and what we have discussed."
Also just to add I did use my credit card and my purchase should be eligible for section 75 protection; however my bank for the above reason refused