^^^ While the Telecommunications Regulations 2000 place restrictions upon businesses recording telephone conversations, private individuals are free to do so as long as the recordings are for their own use and not distributed to others. (There is no requirement to advise the other party to the call that the call is being recorded).
Search Amazon, eBay, etc for 'call recorder' to find suitable landline devices, such as this one:
Amazon.co.uk User Recommendation
You can record any phone call easily. Nowadays there are various apps available that can help you in call recording. Following are some of the apps:
1. Boldbeast Call Recorder.
2. Call Recorder Automatic.