Basically I kiss and number closed this HB8 like a month ago in our student union, she'd bought me a drink that night and I had told her I'd return the favour one day. So we were texting throughout the week and she had made it quite clear she wanted to go for a drink with me but I (foolishly) took the advice of my mates who were like 'no don't go just with her, invite her to come along with us somewhere' so I did and she didnt text back.

Now, 1 month on I'm thinking I could text her and be like 'I haven't forgotten about that drink I owed you' and try to get a day 2. Or should I just forget about it since its been so long? I don't actually mind doing that at all, I just dont want to if I could succeed. What do you guys think?

It depends how much you liked her tbh, if you just text "Hey what's up, lets go get that drink I owe you" its just going to look like you can't meet new girls and you're recycling your conquests.

You said student union, so you're at university, I'd just leave it to chance that you'll meet up again and just mention it on a night out or whatever, use it as an opener. However if you are just plain bored and what a challenge, I'm maybe add her on facebook. Bullshit she came up on your suggested friends or whatever and you remembered her name, I think if you just text, she'd be like who's this? some random I got with a while again? you wouldn't have any space to build attraction again, so I'd say no text, if you must game her do it over facebook so you can a least chat a little, flirt etc.

Hope this helps man.

Yeah makes a lot of sense thank you!

With one girl, i got her number online beginning of Dec, our first date was end of Jan (kiss-closed midway through), and second meet f-closed was beginning of April.
It's already a month later and i haven't seen her yet. Some people are just busy, others work at night and sleep during the day, et cetera, so when you get two of them together...it can be tough to meet.
Might not look it, but it works for me.
For your situation, as i've illustrated above, I wouldn't let the fish go just yet. I would write her, "so what have you been up to, married with 8 kids yet?"