Not wishing to look a gift horse in the mouth, but DS slept 8.5 hours straight through last night. Dd used to feed almost non-stop at his age, so this is a real novelty. However, I am worried that he actually needs to feed more. Durty nappies have slowed down, but there are still plenty of wet ones and no signs of dehydration. He did a lot of cluster feeding yesterday, which I put down to a growth spurt. I got a great sleep, but should I have woken him to feed? Will he just make up the calories in his own time?

I found a lot of mine started sleeping much longer stretches at around 6 to 7 weeks.

Nope - as long as he is feeding efficiently in the daytime there is no need to wake him.
You lucky, lucky woman! My 19 month old is stil waking me to nurse at night - lol!

IKWYM Bibble, my 28 mth old has only recently started to sleep through - althogh she was up at 5am this morning!

DS is still thriving and 9 weeks old now