Sure! Here are some valuable travel tips for visiting London, Liverpool, and Manchester.

Best Time to Visit:
The best time to visit these cities is in the spring (late March to June) and autumn (September to November) when the weather is mild. However, these cities offer unique experiences all year round.

Route and Accessibility:
London, Liverpool, and Manchester are well-connected by road and rail. You can choose to travel by car, coach, or train. There are also numerous domestic and international flights if time is a constraint.

Altitude and Acclimatization:
These cities are not at high altitudes, so there is no need for concern about altitude sickness.

Accommodation and Booking:
Always book your accommodations in advance. There's a wide range of options available, from budget hotels to luxury establishments. Make sure to research and choose an option that suits your budget and needs.

Clothing and Essentials:
Pack according to the season. Summers can get quite warm, so light clothing is recommended. Winters require warm clothing. Carry an umbrella, as rain can be unpredictable.

Health and Safety:
These cities are safe, but it's always a good idea to be aware of your surroundings. Maintain regular hygiene practices and adhere to any health advisories from local authorities.

Local Etiquette and Respect:
The people are friendly and polite. Do remember the famous British decorum and queue etiquette. Respect the culture and traditions, and enjoy local customs and festivals.

Lastly, these cities have a rich cultural and historical heritage, do make time for the museums, galleries, and performances for a memorable experience.