Thanks to the wonders of technology I can log on whilst on hols (its raining out...) but don't have my noltes with me - will send them to the adminsistrators as they may be worth uploading.
Broadly, H.M.Inspectors of Mines annual reports detailed colliery fatal accidents from 1850 to 1914, and for otehr mines (mainly non-ferrous metals and slate) from 1873 to 1914. From 1914 until the cessation of published district reports in 1979 (or so), whilst the inspectors' reports omitted names of the dead and, usually, the names of the mines. Thus to trace fatal accidents in mines after 1914, local newspapers are the most promising source.
The mines inspectorate used to hold the names of men killed and injured (injuries did not usually feature in the published reports) in mines. These were microfilmed and, I gather, the originals no longer exist. A gentleman named Ian Wynstanley bought a set of the microfilms. Later, the inspectorate lost their microfilms I am told, leaving IW with the sole remaining set. IW has a website and can search the data he holds, for which he charges a fee I believe. As the original data on the microfilms was handwritten, transcription by IW includes spelling errors due to difficulty in reading the writing - I have particularly noticed this in Welsh place names.
Individual mines also kept accident registers. Those for collieries that survived into the NCB period were sometimes deposited in county record offices. However, as they were voluminous and repetative (men reported many very small accidents in case they could later claim compensation), county record offices usually preserved only a representative selection of registers.