As ever home made is the best but I always allow for days when unable to stand too long or feeling weary and that's when short cuts can come in handy.
I stumbled across frozen cheese sauce a while ago, comes in segments and you use just the amount you need, with added seasoning and a bit more strong cheese on top it was grand.
When cooking for one sometimes easy is good and can be tasty.
Just an aside, when I do a Bechamel for Lasagne I never add cheese. Just Bay leaves and a half raw onion as it comes to the simmer. In the Winter if I am being posh, I heat the milk first with a clove studded half onion for festive cheer. I also like good Tuna chunks stirred into a bolognese sauce just before dishing out. Spaghetti Tonno lovely.