Sure! Here are some tips for your trip to London, Liverpool, and Manchester:

Best Time to Visit:
The best time to visit London, Liverpool, and Manchester are the spring (late March to early June) and autumn (September to November) months. These periods offer mild weather and fewer crowds. Summer (late June to August) can be quite busy, but offer long daylight hours and numerous festivals.

Route and Accessibility:
All three cities are exceptionally well connected by train, bus, and airports. Train is the most convenient way to travel between these cities.

Altitude and Acclimatization:
As all these cities are at sea level, you don't need to worry about altitude sickness.

Accommodation and Booking:
All cities offer a range of accommodations from budget friendly hostels to luxury hotels. Book in advance to get the best deals, especially if you plan to visit during peak tourist season. Airbnb options are also popular.

Clothing and Essentials:
Pack according to the season. Summers are fairly warm so light clothing is appropriate, while winters can get quite cold so pack warmly. An umbrella or waterproof jacket is essential as rain is common in UK.

Health and Safety:
UK has high standard of healthcare. Pharmacies are easily accessible for basic health needs. UK uses a Type G plug, so carry a travel adapter if needed. Road safety is thorough, follow traffic rules.

Local Etiquette and Respect:
The British are polite and reserved. Queuing is an important part of British culture. When in public places like parks, museums, and restaurants, remember to talk softly as Brits generally speak in low tones. Tipping is customary in restaurants and bars.

Cultural sites and museums in Liverpool and Manchester offer insight into the rich history and culture of these regions while London offers a blend of both historic and modern attractions. Enjoy your trip!