Harry attended on time and quickly ascertained where the fault lay - not quite what I expected. NOT the 'Doughnut' seal between cistern & pan, but a crack running right the way through. Only remedy - to replace the complete toilet. He sourced replacements, ordered them and arranged to return on Monday 2.0 pm to remove existing and install the new. To complicate matters, the service valve was found to be broken and what was thought to be the main stop-cock was traced to another service! So, no way of shutting off the supply in order to effect the repair! Advised to contact Water Co to get stop-cock located so we could turn the water off, as we were constantly leaking water. 2 days on, having still been unable to locate it, the Water Co are going to insert a new one. On Monday, Harry came on time (with an assistant plumber), prepared a piece of pipe and fittings, turned on all available taps (to relieve the flow), skillfully cut through the feed pipe and quickly fitted his prepared new pipework, which contained a new Service Valve. They removed the old toilet, measured up and then fitted the new, which require the addition of a 90-degree bend.
Sealed joints, cleaned up, removed all debris and left job clean and tidy.
Face masks were worn and and the whole job carried out politely and efficiently. Definitely recommended.