I'm not going to comment about the quality of the alternatives you've mentioned because I'm involved with Lencarta...
But I would point out that the Jessops kit you linked to is continuous lighting, not flash. You need flash.
If you can't afford or justify a proper flash kit, have you considered
A single smartflash head with stand
A 80cm 5 in 1 reflector
and a radio trigger (if you haven't already got one)
?
That's what I used, with an 85cm softbox, for the shots
here
These were taken during a talk at the Talk Photography convention, with more time you can do better.