I sympathise with your situation.
As I understand what you're saying, the Education 2030 changes are coming in next academic year, university-wide. Your course has an exemption that means that students currently in their 2nd year can complete their 3rd year under the old system. However, this exception does not apply to the ability (available to previous cohorts) "for people to complete 3rd year remotely by submitting work from their job or placement (if they had alreadu secured one)." Have I got that right? I guess I'm asking whether, from September, you can do your placement year and your 3rd year academic year alongside each other - which you imply was an option in the past. Can you? Or has that never been an option anyway and I've misunderstood what you've meant with "submitting work from their job or placement"?
So, unless anything changes, you'll go on placement next year, being unable to perform your 3rd year studies during that same year (which I suspect you weren't planning on doing anyway and are only mentioning now as it would have avoided the block-teaching method), and will then return to DMU under the new block-teaching method, which in untried and untested, to complete your 3rd academic year. Right?
It there an option to ditch the placement year which you've secured and to complete the third year with the rest of your cohort under the existing system, using the exemption which your course has? Does this has financial implications? You say, "i can't stay in my job (which almost every intern for the last several years has done.... so losing a year's salary & paying accomodation costs)" but I can't work out whether you're talking about losing income during your placement year or losing income during the following year - where you expect to be in the same job, doing your 3rd year remotely.
You ask, "Do i stand any chance of getting some kind of negotiation/exemption?" I suspect the answer to that depends on what you ask for. If you want to return to DMU, having spent a year on placement, and complete the 3rd academic year under the old system - that's not going to happen. If the option ever existed (and it's not clear to whether or not it did) to complete your third academic year remotely - alongside your placement - then that would seem like a reasonable thing for them to let you do, as the rest of your cohort will be studying using the old system during that academic year anyway. I can't help feeling that I must have misunderstood this option though - as the idea of working full-time on a placement whilst also studying full-time remotely seems like an awful lot of work.
You say, "I'm considering calling some other universities that offer my course and seeing if I can move into another 3rd year following my placement year." You should definitely call them and ask, just so you know whether that's an option which is open to you.
(BTW, you're not the first person to post on TSR about the way that DMU have mishandled the move to block teaching under Education 2030, and I'm sure you won't be the last.)