I agree that 3.5 sounds within the normal range (can't remember what the normal ranges are off the top of my head and it does increase by age). Did the GP examine his prostate as I think that is more likely to have triggered the referral than the PSA on it's own? Or has he had a previous, fairly recent PSA and his PSA result has increased? If so, other things can cause a raised PSA, not just prostate cancer. This could include trauma (is one of his fairly active hobbies cycling?) or even a UTI, which could account for the PSA and the haematuria.
I would expect the haematuria to have triggered a two week referral but not specifically for his prostate (and not everything causing haematuria is cancer). I presume he will have a flexible cystoscopy in clinic +/- an examination of his prostate by someone from the urology team. I don't know how quickly he will get seen (depending on the hospital's waiting list) but those results will be available the same time.
I don't know how long the MRI will take, again that will depend on the hospital's waiting list, and it will have to be reported. Those results will not be available the same day.
If they do suspect a prostate cancer, he will probably be listed for a prostate biopsy. Different hospitals have slightly different options available but these usually include the option of a local anaesthetic biopsy or general anaesthetic biopsy and some hospitals have the option of a targeted biopsy, targeting the area/areas of concern highlighted on the MRI. Again, there will be a waiting list and this will depend on your local hospital.
If he does have prostate cancer, it is usually one of the least worst cancers to have.
I hope he is seen soon and both of your minds are put at rest.