Hi, just posting in case anyone wanted to know the outcome.
We got our Havanese pup a month ago at 13 weeks. Heās just turned 4 months today and heās the loveliest ball of fluff. Toilet training is pretty much done, he sleeps through the night (11-7.30am) and while he still has the occasional wee accident in the house in daytime, itās down to us not picking up his signals. We also have accident-free days. He is good around other dogs and people, inquisitive and playful. He very rarely barks or growls (mostly at the broom!), and never at the doorbell (even on Halloween when it rang 100 times). He is not destructive and is very food motivated, which makes training easy. He is learning lots of commands, but we will need to work slowly on him staying alone, as he is a Velcro dog and he follows me everywhere. We are working on that and have started puppy school.
Thank you everyone for your advice, Iām glad I went with a slightly older puppy as he is just wonderful and has been very easy to train. He is fully socialised and is taking absolutely everything in his stride - bus, tube, big dogs, fireworks, hoover etc, nothing fazes him. No regrets whatsoever!
I was also offered an 8 week old Hava puppy by another breeder, but I had a bad vibe about her and the puppy - the house was dirty and chaotic with way too many dogs for the space, lots of barking and adult dogs weeing everywhere. This was from a breeder who has won national titles with her show dogs. It goes to show how important it is to see the puppies in their home environment, and to talk to the breeder at length.