Offered a new job two weeks ago. Duly handed in my notice believing I was on a four week notice period. However. My contract changed when I was promoted so now it's three months. But I told new employer it was four weeks. Spoke to my line manager who said he was sure we could negotiate. New company pressed for an answer so told them end of month (Tuesday after bank holiday). Old company are now saying they can't give me a leaving date until new person in my role is in the company. But also won't give me any additional projects as they know I'm leaving so I'm adding very little value. I'm worried about pissing off new company if I have to move my join date. I'm worried about pissing off current employer if a try to leave at the end of the month. But everything is so up in the air and uncertain. HELP, what do I do???