But that is too simplistic, as there are good vanity publishers who do advertise. It is safer for you to contact one of the professional bodies rather than answer an advertisement. Try the lists of UK Publishers in the Writers' and Artists' Year Book. He will discuss with you the true market potential of what you have written and how you can best present your book to the public. He will simply tell you what services he offers.
All vanity publishers are in the business of making money.
They are not philanthropic. Nor will a genuine one try to give you the false impression that he is. They did pay to see their work in print, but not as one of today's vanity publishers would have you do. He will give you a fee to publish your poem, or offer you a free copy of the anthology, or both. Publishers have to register every book published in the United Kingdom with Whitakers, and also have to send one copy to the British Museum Library, and 5 copies to the Copyright Receipt Office in London, which distributes them to the major universities in England, Wales, Scotland and Northern Ireland.