The law refers to 'an apparatus capable of receiving a television signal'. I worked in An POst, and a colleague of mine who did exactly what you are proposing was prosecuted.
Was it prior to 2009?
Broadcasting Act 2009, Part 9, section 140 "definitions" -
“television set” means any electronic apparatus capable of receiving and exhibiting television broadcasting services broadcast for general reception...
Part 1, section 2 "definitions" -
“broadcasting service” means a service which comprises a compilation of programme material of any description and which is transmitted, relayed or distributed by means of an electronic communications network, directly or indirectly for simultaneous or near-simultaneous reception by the general public, whether that material is actually received or not, and where the programmes are provided in a pre-scheduled and linear order, but does not include:
(a) a service provided in a non-linear manner where each user of the service chooses a programme from a catalogue of programmes, or
(b) other audio and audiovisual services provided by way of the Internet;
(emphases mine)