It's difficult to help the OP without knowing at least some basic info about the dog - age and breed for starters.
Broad suggestions would be to try your local allbreed rescue (google Dog rescue Yourtown) or if your dog is, say, a Cav then type in "cavalier rescue" into google. Most popular breeds have at least one rescue (often working nationwide), and the most popular breeds e.g. Labs, spaniels, doodles etc will have several in different bits of the UK.
General advice on surrendering (and yes it can often be wholly to the dog's advantage - no flaming here). Please make sure you have the dog's paperwork together e.g. vaccination certificates, chip details etc. and these are handed to the person when you do the handover. Also let them know whether dog is spayed/neutered, any allergies, any training and PLEASE be honest about things like behaviour e.g. housetraining. it's not a problem, but it's just so much easier to know to expect issues especially for the foster home who will be looking after them.
Bear in mind that the vast majority of rescue are run by volunteers so don't expect either an instant call back or for your dog to be collected instantly. Especially for rescues where a dog is going into a foster home, transport runs need to be organised and these can often involve co-ordinating several volunteers (no easy job at this time of year, with so many people away on holiday or with kids off).
Rescues will also be struggling as many use boarding kennels to supplement their own arrangements and of course the school summer hols are the busiest time of year for boarding establishments. There is also a noticeable spike in people who abandon and surrender their dogs at this time year, either because they don't want to pay kennel fees when they go on holiday, or they can't cope with both DC and dog at home during the school hols.
Please, please don't try to rehome your dog yourself via social media or FTGH type websites. You will have no idea where your dog could end up and there are some unsavoury uses for dogs when they are easy to get hold of.