It means payable immediately the judgement was issued. So you have breached it because you haven't paid - in fact if you weren't in Court when the judgement was made you breached it before you even knew about it! Because you have breached it the creditor can ask the Court for the charging order. The charging order secures the debt on your house and - if you still don't comply with the judgement or get it varied - the creditor can then ask the Court for an order for sale of the house.
Did you receive the Court papers when the creditor applied for the variation? If so, did you fill in the form and make your �60 per month offer (or some other offer) again? If you ignored it, then that is why the forthwith judgement was made. If you were not notified of the Court application to vary, then you can apply for the judgement to be set aside. If successful, this means the charging order cannot go ahead.
The order you now have is probably an interim charging order, with a date for a Court hearing. You must ask the Court to vary the judgement to something you can afford, and for this to be put onto the final charging order when it is made. If you then comply with it - never being late with a payment - the creditor will not be able to go for an order for sale.
You must do this by filling in the correct forms - including getting the case transferred to your local Court if necessary, & you must attend the hearing. Get advice from your CAB.