In reality I would doubt ATC at a busy airport would allow a downwind ILS and circling approach to be made as it would stuff up their sequencing
In the end it's up to the pilot in command as to what approach is required. ATC wont prevent you from doing this and in the end this will come into their sequencing equation.
ATC will nominate an approach that in their opinion will give you the best chance of a successful approach taking into account all the conditions. If you want something different ask and you WILL receive.