There are presently two main companies who offer coach journeys between London Victoria coach and bus station and these are:
One of the fastest and easiest ways to get to South Wales is by train. Trains to Cardiff, Newport and Swansea leave from London Paddington train station. The journey time between London Paddington and Newport is usually around 1 hour and 45 minutes, with Cardiff just over 2 hours and Swansea around 2 hours and 30 minutes. Prices one-way for a standard ticket, if booked in advance, on average can start from £40 through to £100. The trick is to book as early as possible. I have got tickets for as low as £20 each way via Trainline Online – Book Here!.
The drive from London to South Wales is a relatively straightforward one, provided you do not hit any severe traffic problems, something which is never guaranteed of course.
You can fly into South Wales by flying into Cardiff International Airport (which though is not actually in Cardiff) and is a relatively easy 20 minute ride into central Cardiff or 40 minutes drive to Newport or half an hour to Swansea. There is no airport in Swansea or Newport thus Cardiff airport is the one option. Travelling by train between South Wales and London is a much more pragmatic option but if you do wish to fly, from London, there actually seems to be no direct flights. So the best advice is really to head to Paddington train station and to travel by train. If you do wish to fly, then a private jet from London City Airport is my recommendation.
Cycling is certainly not the way that many people travel between London and South Wales, but there is actually an established and officially laid out route for this cycle journey and this route is known as Route 4! Route 4 will take you from London to Cardiff via Reading, Bath and Bristol and is a little over 400 miles in distance to Cardiff. I have not personally yet cycled the route, but I am really keen to and hope to soon. The route is laid out such that it takes you past many important attractions including Hampton Court, Kennet and Avon Canal and the Roman Baths in Bath. You can learn more about Route 4 from the Sustrans website.
Arriving in Cardiff by boat is certainly quite unusual for most people, but having said that, it is not impossible given that the city is on the water. Cardiff Bay has some moorings and the best advice I can give you to find out more is to follow this link to the Harbour Authority site.
Once in Cardiff, the easiest way the ctiy is to use the hop on hop off tour bus. This bus take you to all of the main attractions including Cardiff Castle, Cardiff Bay and the Millennium Stadium.