This is a friendly gesture.
It means 'good luck'. It is usually followed by the raising of drinking glasses or tea mugs in salute to the person receiving the good luck.
For example: 'Doing your exams? Well then the best of British to you lass!'
A 'doddle' in British slang means something is easy. For example: 'that essay was a doddle!'.
'Let's gave a do' is a British expression meaning 'let's have a party!' For example: 'You're engaged? Let's have a do to celebrate!'
Bladdered is one of the many British slang words that means 'drunk'. For example: 'Look at Jake, he's absolutely bladdered!'
'Brassed off' is British slang meaning 'fed up'. For example: 'I am really brassed off with all this homework!'
If someone says that they validate you as a person, they mean that they consider you to be a worthwhile person.
You mean 'C of E'. This is commonly used to refer to the Church of England. For example: 'The C of E is bankrupt again'.
This probably isn't what you think it is. A cock up in British slang means 'a mistake'. For example: 'I made a total cock up of that pie!'
'That's beastly' in British slang means something or someone is nasty or unpleasant. For example: 'Shaun is a rather beastly fellow!' or 'that smells incredibly beastly!'
It means that you are a nice person.
They are not imitating a bomb, so you can put the phone to the police down. 'Blast' is a British exclamation of surprise or 'oh dear!' For example: 'Oh blast I left the bath running!'
Stop being a mean person.
'C of E' stands for the Church of England, which is the established Christian church in England. When a British person refers to 'C of E,' they are typically talking about this church or someone affiliated with it.