Can’t advise as to who to go with in Aberystwyth but get your ideas straight about what size of van you want before you start phoning for prices as ‘Sprinter’ size covers three very different sizes of van so you won’t know if the prices you are being quoted are like for like.
If you are looking for ‘As large as possible’ then a Transit Jumbo or an Extra Long wheelbase Sprinter that’ll give you a load space about 3.5m long, 1.5 wide, 1,8 tall.
The alternative you might get offered is a Luton type box van – with these ask a lot of questions about size as they are coach-built and vary in size quite a lot from one hire co to another – with load spaces ranging from 3m to 4.2m long. They are wider, taller and squarer than regular vans but carry much less weight – around 800kg (which to illustrate is about the same weight as a Berlingo can carry) compared to 1500kg in a Transit Jumbo. – Worth thinking about as you’ll get weighed at the ferry terminal with a van.