I picked up a Clarke 151 mig welder a couple of years ago and it's a lovely bit of kit to learn on, but i soon got fed up with the disposable gas bottles and switched to a refillable one the missus bought me for Christmas, bless er!
Looking back i wish I'd gone for the Clarke 160 straight out of the box as that comes equipped for refillable cylinders straight away and it would have saved me money wasted on disposables while i learnt
http://www.weldequip.com/clarke-160tm.htm
But then again if I'm being really sensible, I'd have waited even longer and got one of these straight away:
http://www.weldequip.com/parweld-171c-mig.htm !
As others have said, have a good lurk over on
http://www.mig-welding.co.uk/ before you buy anything, as a few of the other Sammio builders are finding that cheap ARC welders are fine for what we want. That may be different for you Marlin boys, but i thought it worth mentioning