She's asked me to come round to hers for the first date - what does this mean?

If she explicitly says "I want you to interact with my vagina - sexually" then she probably wants to have sex. If not, it doesn't mean anything unless she clearly states otherwise...

Sometimes people just can't afford to go out and are trusting enough that they don't think you'll murder them in their own home.

So someone I have been talking with has invited me to hers for the first date as she is a bit broke now and traveling into London is not possible. How do I interpret this as she said we could chill on the sofa with some wine and have some cuddles and chat.....

How do I approach this?

Sounds like she wants a date-date (as in "Cuddles on the sofa" isn't a euthamism for something else) especially since you said she's broke so maybe she wishes you could go on a big fancy, romantic date but she can't afford it and doesn't want you paying too much, I'm sure she literally does just want to watch a movie at hers and have something to eat and drink, nothing sexual.
I recently went to a guys house and he said we'd have a date at his house- at this point I made sure to explain to him I wasn't just looking for sex and only wanted to hang out and maybe cuddle or kiss and yeahh well he thought I meant as in sex but I didn't and it was extremely awkward cuz he kept trying to touch me and it really upset me so yeah things are over with us because of it so it's important to make sure you don't do this, just because a girl wants to hang out at your/her house does NOT mean she's just looking for sex.
(Sorry having a bit of a rant cuz I'm still pissed about that guy)