You're probably correct here. I'm just trying to see why he'd be taking Lydia along if his intention is to simply get away. I'd think she'd tend to slow him down, if anything.

If we look at that motive alone, there could be one reason for doing so. If he got the idea to make people think they'd headed for the Scottish border (with the help of Lydia's letter), they might not look for him in London. That would definitely buy him some time to hid out before moving on and setting himself up somewhere else.

Lydia, however, might complicate things, or at least drain what resources he had (after he'd finished fleecing her). I wouldn't put it past him for Lydia to wake up one morning (or return from shopping) to find Wickham had grabbed up what he could and disappeared. Off to find fresh territory while she's on her own to find a way home or fend for herself.