There's no need to buy a box and then use an external modulator (be it a stand-alone or part of something like a VCR or analogue satellite receiver or something), my two Humax F2 Fox-T boxes I picked up for a total of £15 (one 35 at a carboot, the other £10 at Cash Converters) have analogue modulators so can be used on older TVs with only UHF input, and they're compatible with the 8k standard...
I do have an OnDigital Nokia Mediamaster 9850T somewhere, a refurbished model where they sprayed it silver and removed any external hints that it was an On box, but the software they couldn't change given that the OS was owned by On and subsequently ITV digital, and no-one has the rights to alter it to allow any updates, and in this day and age, very few people are interested in updating them sadly, even people who like modifying software for additional features or enhancements don't do anything for these boxes...
That reminds me, must dig out my MediaMaster 9800S (Digital satellite box)...