Toilet is early 70s, Twyford, with ceramic & metal (far from shiny and new) innards. I've spoken with Twyford to ask if they carry suitable replacement parts but they tell me that the tail size has changed since then and so nothing they have (or have had for decades) will fit.

Does anyone know of a suitable retrofit please?

I realise a dual flush system wouldn't be possible, given the front lever layout, but just want to know whether there is a way to bring it back to decent condition or instead that I need to replace the whole toilet etc.

Thanks  

Here are 3 photos of the unit. When I look at them now they don't look too clear, but hope they are OK. Hopefully you can see the type of unit (porcelain insides, no isolation valve - needs fitting) and the general state of the inlet valve area. Works, but for how long?

Thanks thescruff. Not tried this before, so might go with a handyman/plumber. I've watched videos and all looks straightforward but don't want to find I get something wrong and have water gushing