British Infection Association published a UK position statement on Lyme borreliosis in 2011 and NICE Guideline (NG95) on diagnosis and treatment was published in April 2018.  The guidance has been updated in line with NICE, with any recommendations differing from NICE further explained in a footnote.  Please note the higher doses of amoxicillin throughout and the higher dose of doxycycline for CNS disease.
Link to Scottish Microbiology Reference Laboratory: Lyme disease and tick-borne infections User manual 2021.
The rash of Lyme disease is an expanding erythematous rash usually at site of tick bite, appearing 3 to 30 days after tick attachment and reaching 5cm in diameter.  A lesion appearing within 24 hours of tick attachment and resolving in 48 hours is likely to be a hypersensitivity reaction.
If diagnostic or management uncertainty please discuss with local Microbiology, Infectious Diseases (ID) or Paediatric consultants. Specialist advice can be obtained from the National Reference Lab – see user manual for contact information.
Discuss management of Lyme disease in children and young people with a specialist, unless they have a single erythema migrans lesion with no other symptoms, see NICE recommendation 1.3.2. Children weighing above the specified amounts should be treated with the dose for adults and children aged over 12 years.
Ask women (including young women under 18) if they might be pregnant before offering antibiotic treatment for Lyme disease (see NICE recommendation 1.3.18 on treatment in pregnancy). For Lyme disease suspected during pregnancy, use appropriate antibiotics for stage of pregnancy.

Erythromycin should not be used to treat Lyme disease.