I have heard that not all UK GPs will prescribe test strips, but if you want to seek to persuade them post-op not sure if you have seen the National Institute for Care Excellence (or something like that) report they produced in 2014, which recommends self testing as leading to fewer complications from Warfarin management. I did a quick summary to persuade my GP, but ended up not needing it as he was very much in favour of this - and self testing is much cheaper for the NHS too, when compared with the cost of staff and lab tests. See
http://bit.ly/NICEreport if useful.