Flea treatment/preventative for dogs

[AliceInUnderpants]

The vet issued Frontline for our pup (I know it's said to be crap, but because the vet issued it and it's always been fine for our cat (preventative - never needed to treat existing fleas) I thought I'd give it a go) Second time we had to use it after an outbreak, so I took the dog to be weighed to check she was still within the weight range, all fine. It cleared up the fleas and I treated the whole house too.
Now, four weeks later, she's got bloody fleas again!! So, obviously, frontline isn't doing the job. I've got one last application here I'm going to apply for temporary relief for the poppet whilst I get my hands on something else.

What's recommended these days? Advocate? Advantage? Something else? (Topical would be preferred, but I can give tablets if necessary).

She's a 12 month old GSD cross if that makes a difference, around the 20kg mark.

I have always used Billy No Mates, it's a herbal supplement added to their food.
Contains neem oil among other things, makes dog smell lovely but it's extremely off-putting to fleas and ticks.
Never had any on our dogs.

We also had fleas with Front line.

Have since moved to Advantage and not had them for around three years.

We use Advocate, no fleas since swapping from Frontline.

We use Advocate too. Our vet says most of the fleas around here are resistant to Frontline and doesn't recommend it.

Neem oil diluted in a carrier oil, I use almond oil dabbed on behind ears & near tail. You can dilute it in water with a little soft soap as a coat dressing too.