Which Digital timer switch for Boiler immersion

I have found that lighthub on amazon is about the best. It's a switch fuse spur that if fitted correctly will have less chance of burning out. Please note that it would be best fitted by a qualified and certified installer.

I would recommend time guard timer very good quality little pricey but you your money’s worth you will need qualified electrician as the last chap said ok

Any 13 amp timer should work. My question is why two have failed, what failed in them, is your circuit of good quality? There are many question which would require answers before I fitted anything for you.

I would suggest avoiding a 13A timer or a fused spur (which will also be rated at 13A) as some others have suggested, voltage in the UK varies (permitted supply variation is 230 -6% to +10%) and dependent on what it is coming into your home a 3KW immersion heater may be drawing more than 13A (230-6%=216, 3000/216=13.8A,) stressing the timer or fused spur and putting your home at risk of fire. for a simple on/off switch we'd usually install a 20A rated double pole switch. As someone else said, Timeguard are fairly good and do a range of immersion timers, most rated at 16A, if you want to go higher end then the Heatmiser Neostat-E can be set to timeswitch only and will switch up to 16A and has a smartphone app feature if you get the hub too. Either of those options will require actual wiring work so consult an electrician who is a member of a Competent Persons Scheme.