Seymour is probably going to be Ian's greatest adversary for Lena's affections. Forget Axel, Mike, Jeremy or Jack, they're just temporary distractions compared to Seymour. He is the one, that Ian will ultimately have to destroy, to hold on to Lena. Because you can bet he will try to destroy Ian, if he doesn't give way. So sorry, I don't think that friendship is going to last very long.
Why do think Seymour is being so nice to Ian and Lena? He's making them both dependant on him, so he can control them. Lena's entire modelling career, is now dependant on Seymour. Most people won't work with her, if he doesn't want it. He's got her off Stalkfap, which might have been a very lucrative alternative source of income. She's blacklisted from working as a waitress. He even tried to take over Molly and Ed's cafe. On top of that he's paying for her Mother's expensive medical treatment.