Thanks very much to you both. Absolutely no offence intended at all - I hear what you say and will heed the advice given.

For info, I have managed to update the mapset to 910.4952. Now need to roadtest it. Thanks greatly for your advice and guidance - I have learnt and am still learning a lot. This is my first satnav unit (as you've probably realised given my naivety and unintentionally poor etiquette) and I'm beginning to see that the weird and wonderful world of TomTom GPS systems takes a lot of learning and reading. I'm up for the challenge as I further explore the limits of my 'antique' unit. Once again, apologies for acting like a naive newbie. Lesson learnt..