Greenhouse question

I have recently aquired another greenhouse to go in the back garden, our circular 6x6 just is not big enough for everything we would like to grow. The one we are now getting is a 6x8 normal rectangle shape but i dont know what to do about the base. 
 I know i could put a concrete base down then put the greenhouse on blocks, was wondering if there are any universal aluminium bases available that anybody recomends?

Totty

I'm about to get a second-hand 8x6 too, and was put off the the vast amout of concrete/ effort a base would require.

Instead I've been advised to use blocks http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=9273668&ecamp=trf-005&CAWELAID=266890923 underneath the perimeter of the g/h, sunk 3/4 into the soil and mortared. The g/h can then be fastened to this, and the interior covered with weed suppressant.  Makes for a fairly easy, cheap and semi-permanent job.

Hope this helps.