I was going to recommend a Cavalier King Charles Spaniel. Our last one was lovely and we now have an 8mth old puppy. They are perfect family pets. Very adaptable, good with other animals and children. They can manage really long energetic walks or equally happy with shorter ones.
There are two provisos however.
1/they do not do well if left for hours alone. They want companionship a lot.
2/ I absolutely would not buy one unless it confirms to the Kennel Club Heart Clear Scheme as a minimum.
CKCS are 20x more likely to get early onset mitral valve disease (MVD) than any other breed. Very sadly our last dog had to be put to sleep at the age of 8. The scheme wasn't in place when we got him. Check out Cavalier Health Matters website online for lots of info about the scheme. As most cavs don't develop MVD until they are 5, you should ensure that both parents are Doppler heart tested with a green/clear result if they are under 5. It's also helpful to have the history of the grandparents. Any pup should come with certificates.
Also Google syringomyelia, which they can be prone to, especially through poor breeding.
Many online sites claim that their puppies have been extensively DNA health tested and Kennel Club registered. This means very little. Anyone can register with the KC. DNA tested only identifies those conditions caused by one gene. As syringomyelia and MVD are polygenic, they cannot be detected through DNA testing. However, the heart clear scheme has been shown to reduce the risk of MVD by 75%.
Now here comes the pricey bit. To get a well tested heart clear dog it will cost you. Expect to pay between 2-3k. However, our last dog cost us £4k in vets bills in the last 6 months of his life, not to mention his suffering and the heartache. So, in my view it is well worth spending money upfront.
Champ dogs, The Kennel Club Assured Breeders Scheme and The Cavalier Club UK provide info about good breeders puppies. The cavalier club have regional coordinators that can put you in touch with your closest breeders. There is also a Cavaliers UK FB group.
Do not buy from pets4homes and similar sites online. Most are from puppy farms, which have been placed in residential properties..The RSPCA has great advice on how to avoid inadvertently buying a farmed puppy. Also avoid at all costs Kelly's Kennels and Douglas Hall Kennels as they are Irish puppy farmers (fully licensed), that export puppies into the country using a pet shop trade loophole in the law (which should hopefully soon be rectified).
I cannot speak highly enough of this breed. They really are lovely dogs with less behavioural problems than cockers. Avoid cavalier crossbreeds for the most part (with a few exceptions) . Research has shown them to be no healthier and breeders tend not to have the parents heart tested on the cavi side.
I hope that this helps. I enclose a picture of my beautiful little 8mth old pup.