We are 4 people staying at Hua Hin for a few days in late January who have Hotel reservations in Koh Samui,any suggestions as to how we might travel between the two places?

You could take the night train leaving HH at 23.10 and arriving in Surat Thani
at 6.40. You will be able to catch the 7.30 bus to the ferry pier for the boat, arriving Samui around 10.30. For the train you have the choice of 1st or 2nd class sleeper berths. A train/bus/ferry ticket can also be bought.

I'd get a driver to go to BKK and take Bangkok Air to Ko Samui. More money than Scotters suggestions, but a lot faster.

Although not very comfortable there are buses from Hua Hin connecting with Ferry boats, usualy leave around 9.30 pm, also there is twice daily Lomprayah which is bus to Chumphon and then Jet-Cat that island hops to Koh Tao, KPG and then Samui.

You can also get a car and driver to take you to the pier for the Samui ferry boats, that would take about 5 hours easy drive from Hua Hin on dual highway.

you could hire a driver in HH and have him drive you south to the ferry pier mentioned above...

i would be inclined to go back to bkk and fly quite honestly...i think the drive south would take quite a while, but perhaps james will tell us??

I have just seen it is 4 of you, in that case just as well to get a nice station wagon or nice Land Cruiser type vehicle, drive to the freeey boat near Surat Thani, normal car with driver would be about B 3-4,000 for all of you, more luxury vehicle/mini van roughly about B 5,000 tops, divide that by 4 and it's a comfortable and easy way, you can even get them to take you right to your Samui accommodation using the car ferry.
That is easy to arrange in Hua Hin.

James way is the best and about the same cost of 4 1st class train/bus/ferry tickets. Going back to Bangkok and flyin would be expensive, with just the airfare being around 15000 baht for 4.

how long would the drive be however??

It's about 5 hours to Don Suk for the ferry, less if getting just the fast boat from Surat Thani town. The road is dual highway all the way, it would take a good 2.5 to 3 hrs to the airport, 1 hour check in plus flight, the flight way would be perhaps 2 hours faster but for 4 it is a whole lot cheaper. Another is to take a driver to Chumphon, about 3 hrs 15 mins and get the afternoon Jet-Cat, though that takes a while as it stops at Koh tao and Koh Phangan it does give some island spotting on the way.

You can go to the website http://www.travel-huahin.com/transfer.htm and book your transfer(bus+boat)to Ko Samui via Chumphon there. You just pay when you stay in Hua Hin to Ken Diamond Tour direct. (between Sofitel and Hilton Hotel)