By the way, a couple of other things to bear in mind:
1) If the base of controlled airspace is 1,500ft, you may find loads of GA traffic trying to squeeze under as well. Although I'm not a paramotor pilot (yet), I do have a PPL, and would recommend that you stay as low as possible, say 500ft. GA traffic will probably bunch between 1,000ft & 1,500ft.
2) You may provide a radar return to ATC. As you probably don't have a transponder, ATC will not know if you are in controlled airspace or not. It might be helpful to warn them of your presence on frequency.