In this scenario, you have to be aware that the tenants holding leasehold interests in your freehold (flat owners) may be eligible to exercise their Section 5 Right of First Refusal (you have to offer them the chance to buy the freehold). Ensure that your auction house is aware of the leasehold interests, they should then advise you that the timescales before any auction are much larger regarding this possibility - in particular you have to start by serving a Section 5 Notice between 4 and 6 months before the auction takes place.