If you're in a 9T jet that rotates in 15-25s (I see this happen quite a lot), then most probably you'll never enter the path of 738's vortex - you simply outperform him.
Yesterday 22:49
Having given this some thought over the last few days and spoke to a pal of mine who is a Captain on the 738 and with several others more experienced then myself I have had confirmed what I had suspected. I will almost always out perform the 738.
Having had a terrifing wake turbulance experience some years ago which nearly cost me and 11 pax their lives I am, as I am sure you will understand, a little more aware of the consiquences of such an encounter.
Please always tell the tower if you believe that you will require more Vortex spacing than they need to give you (presumably when you are flying outside UK) before you enter the runway.
And that is really my point. If I don't know he is not going to give it to me then I dont know I need to ask. But lesson learned, I will be more aware next time.