I got it two years ago. It's less than five pounds as far as I recall. It's the number 28 or X28. It's just a regular local bus and it takes about 45 or 60 minutes.
If you're going on Friday there'll be a HUGE queue at the bus stop outside Taunten train station for that bus but if you walk further up into Taunten you can hop on at an earlier stop on the route. As far as I remember you should hop on at a stop on the right side of the road as you walk away from the station. Then sit on the bus and wave at the massive queue back at the station and carry on to Minehead.
thanks again (see above)