Awaiting surgery via NHS

[tia92 7]

Currently waiting for gastric bypass procedure , I have an appointment in September which will involve me having a comprehensive medical inc seeing the Anethetist , weigh myself meet the nurse , surgeon , blood tests and psychiatric evaluation . Does any one know roughly the time between going to this evaluation and the operation itself as still have not received a surgery date yet and thought there might be a time frame that can't be exceeded between the evaluation and actual surgery inc pre op diet . As circumstances and body may change ... A less complicated way of explaining what I mean is that all the results from the evaluation made on me could become invalid or wrong if operation is not preformed relatively soon after my medical ....?? Any one else know?