Is a train-daytrip from London to Manchester feasible?

I am visiting London next week, but only today I found out that I may need to go up to Manchester too. Since I have already made all the arrangements for the trip thinking that I was to stay exclusively in London, I was wondering if I could possibly use the National Rail Services for a day trip to Manchester and back.

I have already checked the National Rail Services website, so I know that the trip lasts between two and a half to four hours.

- So, the idea seems feasible, but is it really?

- Are the National Rail Services trustworthy?

- How possible is that I encounter delays that may lead to my staying overnight to Manchester? Or is a day trip from London to Manchester (or of equal distance) and back something quite usual for the UK residents?

- Do I have to book tickets in advance?

- Is there anything else that I should bear in mind before taking a train trip in the UK?

My question may seem silly, but please note that I am not a UK resident and in my country the rail services are far poorer compared to the UK’s.

Thank you in advance:)