IFE questions.......

Hello
I was going to try and buy an exit row seat for my outbound flight to SFO once I get to the airport (paid for PE for return journey but couldn't afford the upgrade to PE for outbound as well [:#])
My connecting flight will get me to LHR about 3.5 hours prior to flight - will that be enough time for getting the exit seat?
Also - I have seen a couple of reports on here that say the IFE Vport systems at exit rows and bulkheads are more likely to have technical problems - is that accurate or are they the same as the rest???
Thanks
Jo
I was going to try and buy an exit row seat for my outbound flight to SFO once I get to the airport (paid for PE for return journey but couldn't afford the upgrade to PE for outbound as well [:#])
My connecting flight will get me to LHR about 3.5 hours prior to flight - will that be enough time for getting the exit seat?
Also - I have seen a couple of reports on here that say the IFE Vport systems at exit rows and bulkheads are more likely to have technical problems - is that accurate or are they the same as the rest???
Thanks
Jo