1. Know in advance where you are going:
Google Maps is your best source of information for a first time visitor to the UK. After that, the use of National Rail app (for trains), Megabus UK or National Express websites (for buses), and traveline.cymru (for travel in and around Wales) will also be quite useful.
2. Getting to campus from the airport:
If you are an international student arriving in Cardiff International Airport, contact the IISA days beforehand for a free taxi service from the airport to Treforest.
If you come into the country in groups (and I know some students do that because they come from the same education agency), it is best to settle accommodation in advance.
Have a look around for the nearest grocery store for basic necessities, or superstore for long-term needs. Within five miles of Treforest Campus, you should find a Sainsbury's, a Tesco Direct, a Tesco Extra, a Lidl, and Iceland, and a B&M.
Be sure to attend International Welcome Programme to get to know more about the community, the services that they could find in and around their campuses, and meet GAs that will guide them well.