Given the fact that you have an airline job IN YOUR POCKET, and are not in debt for it you now have the enviable opportunity to do anything you damn well please. My advice, don't go into debt for an instructor rating. In fact, don't go into debt at all. Presumably you won't see any direct benefit from joining BA with a couple hundred more hours?
Get a well paying construction or bartending job- something you won't feel too much loyalty to, and make some money! Get up a nice savings to carry you through the first few years at BA when you are poverty-paid newhire. Once you've saved up a couple grand and then some go take 2 months and travel somewhere, be a ski bum or beach bum. See the world, enjoy life and visit countries for the fun of it.
Sure, once you get into BA you'll have all the travel you can stand, but it will be "airports of the world". And as with any seniority based system, there is no room for extended vacations once you are on that train buddy. I say take this time while you have it, instead of beating your brains out trying to get a flying job (or going into debt- which you'll regret). Your time will come!!