I live in Preston and a year or so back we found a decent entry into this place. Spent quite a few exciting evenings and a full Saturday inside exploring but the access was well secured pretty quickly. I have no idea how to currently get in, but imagine you will have to be quick to catch it. Great building with a strange mixture of chapel, hospital and old people's home, all sadly getting slowly destroyed.
Also, if you're inside, try and find the basement which is accessible from the inner courtyard, rather than the street facing gated courtyard. The entrance is quite hidden (and re-hidden by us) and took us a while to figure out, but we knew there must be one due to the low level windows. There are boxes and boxes of photos down there which are really quite interesting. Unfortunately not a morgue which we were hoping to find! Still worth it as I doubt many people have been down there at all in recent years.