I wonder to what extent the negotiations between Universal and DCMS are about money, and to what extent they are about other things? Obviously this is not a straightforward discussion with Universal simply saying "give us £XXX million and we'll invest £10 billion in a new theme park". Even if it's a purely financial negotiation there will be many key stakeholders that will need to be involved, such as other government departments (transport, housing, business, treasury for example); national agencies such as Highways, Network Rail, East West Rail; local authorities such as Bedford and the other local councils which will be directly impacted by this development; and probably more organisations once you get in to the fine detail.
But I don't think this is just a financial negotiation, I think it is much more complicated than that, and accounts for why this part of the process is taking months and months. What makes this proposal unique is the fact that planning permission will be granted by central government via a Special Development Order approved as secondary legislation in Parliament. I can't find any other example of a commercial development on this scale being approved by a SDO. I doubt that government will give Universal approval for planning permission without having a pretty good idea of what Universal actually want to develop. If Universal were applying for planning permission in the usual way via the local authority they would have to submit very detailed plans so the local council could consider all aspects of the development before giving approval. Why would a unique planning process by central government be any different? I hope that it isn't - as much as I'm looking forward to Universal GB I don't think the company should be given carte blanche to do whatever it wants. So perhaps the months that have passed since this negotiation has started has partly been accounted for by Universal developing much more detailed proposals that the government needs to consider before it gives the green light? I sure the DCMS aren't interested in whether it Minions or Ghostbusters that provide the IP for a particular attraction, but knowing an approximate layout of the site, the size of the buildings, the sight lines from local housing, how it meets environmental regulations, power, water and sewerage requirements, transport flows, economic projections, etc, etc, etc, should all be considered before agreeing to planning permission. This is exactly what a local authority would need to consider via traditional planning applications, and I think DCMS on behalf of national government is probably going through a similar process. Given the unique nature of these negotiations, perhaps this is also a bit of a process of discovery about what is necessary as there's no handbook dedicated to how the government approves this kind of large scale commercial venture.