Sapper, double-check the result. On PATCHS, the PSA result screen shows 4.06 as the threshold for 'normal' so could it be the same on MyChart; e.g. the 4.06 is a statement and not your actual reading?
If that is your reading, worth trying to get another test before your Addenbrookes appointment just in case it is an error but your urologist should refer you straight to oncology when you see him / her next week.