Hi Kirsty. I’ve run a number of author events in our community library which are very popular. We are based on the South Coast about a couple hours by train from London. My suggestion would be to seek out local authors. They are nearly always self published and keen to give talks about their work. Generous with their time as it is invariably down to them, rather than a publisher, to sell books and promote their work. Also, being local they rarely ask for a fee. I’ve tracked most down by contacting local writers groups. Generally a small community who support each other. I’ve had less success with Best Seller authors and can only suggest contacting their agents or scanning their websites for contact details. Although in my experience few respond! Those I have managed to secure only claim travel expenses rather than a flat fee. I hope that helps.
Regards – Kate