Applying for accomodation before firming

Hi,

I haven't firmed anywhere yet as I'm still deciding where to go, but I saw a post in the Student Room from last year where someone said that they applied for accommodation before firming anywhere. Is this possible?

Secondly, I went on the accommodation website for applying and they said I needed my Uni of Manchester ID? I've looked on my offer letter on UCAS for this but I can't find it anywhere. Does anyone know where I can find it?

Thanks

Generally you'd have to decide before applying for accomodation