The Minor Planet Center will be able to provide an Ephemeris via web page https://minorplanetcenter.net/iau/MPEph/MPEph.html. You will need to use C/1980 Y2 for the comet name and then add the date you want such as the discovery date of 19801225 and then an ephemeris will be created such as that below for a geocentric observer. You can change the observer location by adding an Observatory Code (e.g. 000 for Greenwich which will be sufficient for the UK).
Lars, The ephemeris from the MPC that Peter gave is about as good as it gets. Any differences in the 1981 ephemeris will be due to a different epoch (B1950 vs J2000) and fewer observations. I’ve attached an ephemeris from JPL Horizons wich is very similar to the MPC one. I’ve also attached a scan of BAA Circular 615 from 1981 March 4 which includes an ephemeris based on only 12 positions over a short arc so you can compare.