Takeovers are normally either hostile or non-hostile.
In non-hostile takeovers you get:
a) break fees
b) "no shop, no talk" agreement
c) some line about "in the absence of a superior offer, directors recommend shareholders accept the offer..."
None of that in this announcement. Lack of a & b good for shareholders. No c is a worry.
I can't see anything in this announcement that makes another offer from a 3rd party unattractive so it's well & truly in their court now.
We also need to know if IG intends to vote his shares.