David,
I think you are quite right, not a great deal of investment is likely to be needed. However, there will be ongoing maintenance and renewal (weren't the air bridges second-hand?) and I've a feeling STN's been getting tattier over the last 3/4 years while the uncertainty over its future was being resolved.
The biggest issue is the purchaser putting up £1,000,000,000 of someone else's money. That has to be paid for (interest + repayments) before dividends can be paid to the owner or profits re-invested in the facilities.