What is the legal situation regarding text spammers?
The law that covers text and E-mail spamming, along with pre-recorded phone adverts, is the Privacy and Electronic Communications (EC Directive) Regulations 2003 which is enforced by the Information Commissioner's Office (ICO).

In particular section 22 states:

Except in the circumstances referred to in paragraph (3), a person shall neither transmit, nor instigate the transmission of, unsolicited communications for the purposes of direct marketing by means of electronic mail unless the recipient of the electronic mail has previously notified the sender that he consents for the time being to such communications being sent by, or at the instigation of, the sender.
And section 2 makes it clear that this covers text messages, as well as pre-recorded phone messages, when it states:
"electronic mail" means any text, voice, sound or image message sent over a public electronic communications network which can be stored in the network or in the recipient's terminal equipment until it is collected by the recipient and includes messages sent using a short message service;

In addition to the above, section 23 states that the adverts cannot be anonymous and there must be a way to opt-out:

A person shall neither transmit, nor instigate the transmission of, a communication for the purposes of direct marketing by means of electronic mail-

(a)where the identity of the person on whose behalf the communication has been sent has been disguised or concealed; or

(b)where a valid address to which the recipient of the communication may send a request that such communications cease has not been provided.

Section 30 allows for damages to be claimed:
A person who suffers damage by reason of any contravention of any of the requirements of these Regulations by any other person shall be entitled to bring proceedings for compensation from that other person for that damage.
There are very narrow circumstances in which text/E-mail adverts can legally be sent. This is made clear in a quote from the ICO which summarises the above laws as follows:
Section 22 of the PECR says that unsolicited direct marketing text messages cannot be sent to individual subscribers (including sole traders and non-limited liability partnerships) without prior consent. There is a very limited exception to this rule where an organisation can satisfy all of the following criteria:
  • the organisation has collected the individual's phone number whilst selling/negotiating to sell something to the individual; and
  • the organisation only sends direct marketing text messages about its own goods or services similar to those originally sold; and
  • the individual was able to opt out (free of charge) from receiving marketing in the original transaction, and in each subsequent marketing text message
Section 23 says that senders must not conceal their identity when sending direct marketing text messages to any subscriber and must provide a valid marketing opt out address.