Billing form does not preload defaults when changing processor

I observed while testing paypal that if you change billing block it doesn't get the default address details. I suspect this is not new to 4.7. However, the fix is not tricky - except that I'm not sure the best way approach in CRM/common/PaymentBlock.tpl

I've altered the payment form such that it reacts to the normal url parameters of cid & cs (checksum)

So, I guess the calling form needs to check first whether it 'knows' the cid by virtue of it being selected on the form. Alternatively does the url contain cid or cs. If not then it doesn't need to determine the logged in user as the form will fall back on that anyway.

@Coleman - I'm going to add the php part of this & then try to pin you down to determine the template / js part