They havent defined the details of the entitlement offer yet,...

They havent defined the details of the entitlement offer yet, looks like that will happen first thing in january. But after that they should send you a peesonalised form or link that details exactly how many shares you've been allocated in the offer (usually its 1 share for every X held, where X is likely to be 11 or 12). Then similar to a SPP you transfer them the required money. They may also allow you to request more than your entitlement (by transferring a larger sum of money) and depending on the uptake, you could end up with more than your allocation. But this is all just based on rights issues ive participated in previously, IVZ could choose to structure it differently.