Okay this is easy to sort out sparklie may have typed the 'show as link' wrong but the link that actually jumps you to the site is correct.
About the 3k fills. the h-pac guys know what they are doing when it comes to filling bottles, so they only fill up to 3k on a 3k bottle [to many 3k's here methinks]. If you have a higher preassure bottle then thier shiney red fire engine [or have they changed it to the 4 1/2 tonne truck now] has the capacity to fill to it.
word of warning though, make sure that your bottle is HSE tested and in date. If its DOT or out of date then sorry its no fill for you, unless you can find somebody nice with a scuba tank.
Oh and try to camp as far away from them as you can [unlike me at kennys] as they start the compressors up at 5 am. And although they are nice guys, they did take the piss out of my attempt to make a pavement pizza on the Sunday morning.