I'm not sure who sings it but you can download it from the Lloyds TSB website. You need to select the 'for the journey' section. I have been reliably informed, by my brother and sister who both work there, that it was especially composed for the company. Hope this helps.
OH i love this tune!! My little nephew who is the apple of my eye always stops to watch it and is completely mesmerised when its on tv, he is only one!! He has not been well and we were worried about him and whenever this song came on i wanted to burst into tears. NOw he is better and whenver he is around at mine I always play this for him and i have it stored in my favourites