Withdraw or ask for more time

Hello there,
I have a situation here and I hope someone knowledgeable can offer an insight.
I am currently enrolled with a HEI as a PhD student, self sponsored. However, I have now been offered a 50% scholarship with another one, and I would like to take it. Unfortunately due to the new rules, i will need to apply for a new visa, and I have got everything ready for this.
I am now confused on how to leave my current provider before applying for the visa, as my next installment is due and I don't want to pay it as I will be leaving.
Should i just ignore them? As they said if i don't pay on a certain date i will be automatically withdrawn? Should I tell them am withdrawing and transfering to another school? Or should I tell them i need more time to source funds?
Am just worried as what will happen if I don't get the new visa and i have already withdrawn. Will i be allowed to go back to them if i don't get the new visa? Or will UKBA cancel my current visa?
I ama sorry that this is too long, but any advice is welcome.

You should inform your current sponsor about your intention and they should withdraw your sponsorship and UKBA would write to you curtailing your leave to 60 days then you would need to make a fresh application within this period with all the relevant documents from your new sponsor.

Note: You don't have to wait for UKBA to write to you and can make a new application at any point after you have informed your current sponsor.