I've got a 9-hour connection at LHR my BA flights arriving/departing T5. Flying WT but hold AA OW Emerald status so know I can access various BA departure lounges, including the First Class facility. However, also recognize OW status will not give me access to the BA Arrivals Lounge. So... Assuming I have my onward boarding pass, I can use the First Class facility (shower, have breakfast) but will it then be possible to head to immigration and go land side to get into London? Do arriving and departing passengers at T5 intermingle as in the other LHR terminals, or are they segregated as at US and Canadian airports? Thanks for any guidance that may be provided.