Thanks for all your input.
@ MrsKK, the rennet I use is powder which I'm finding difficult to dose for these small home batches, I was actually trying to find out how I can get liquid rennet
@ Sallymc, I might try your method without rennet and see if I can get that to work. I'm working on getting a better source of milk and would love to end up with jersey milk.
@ Vina, Well, I've now looked that up and it does look like freezing this particular rennet is not the right thing to do so that may go a long way in explaining my failures, thanks for the feedback on this.
Now a new problem, I've been making batches of simple cheese, just skim milk, rennet and culture then drain the curds and add cream for a kind of cream cheese. The last two batches (in the last two days) have gone funny with a lot of bubbles on top of the vat when it should be ready for draining, it doesn't look right. I've simultaneusly made yogurt with milk from the same source with no problem. Is this poor hygiene or perhaps my cheese cultures have been "infected"?