This: https://www.argos.co.uk/product/5820539 but make sure that it is the lawn version of Weedol because they do another version which will also kill the grass. Spray it directly onto the weeds.
Not worried, lawn looks fine, just like weed free, I do cut the grass every 2 weeks so it's all tidy just odds weeds started coming back, nothing new really.Why worry?
Some weeds are actually helpful herbs that flower and attract bees.
Mow it if you like, when they get tangly and tall but let them grow and see how your lawn can bloom.
Taking a laissez faire approach can reap unexpected benefits as you become the accidental gardener.