There is no freedom of speech in the UK if you can be arrested for tweeting something that "annoys" another person...
I think there is some confusion here. As far as I can ascertain, that part of the 2003 Communications Act refers to the making of silent telephone calls.
" It was declared an offence to "persistently make use of a public electronic communications network for the purpose of causing annoyance, inconvenience or needless anxiety". Ofcom subsequently developed policies to reduce the number of silent telephone calls."
What the TheOther is asking about refers to Section 127 of that act, malicious communications.
" Section 127 of the act makes it an offence to send a message that is grossly offensive or of an indecent, obscene or menacing character over a public electronic communications network. The section replaced section 43 of the Telecommunications Act 1984 and is drafted as widely as its predecessor. The section has been used controversially to prosecute users of social media in cases such as the Twitter Joke Trial and Facebook comments concerning the murder of April Jones.".
I wondered who and how many are really sentenced under that law to constitute a suppression of free speech
More than I thought there would be, but IMO, if you're a normal, well-balanced person who isn't a troll sending malicious and nasty messages online, you more than likely have nothing to fear ;-)
Have a read of this: