2006 diesel Sport – lack of power?

2006 Sport 117,619 miles on the clock. 90% of the mileage travelling on traffic free roads and motorways in France/Spain. Serviced every year by a trusted component garage. Only use premium diesel. The acceleration is not what it used to me (perhaps only to be expected https://www.rrsport.co.uk/forum/images/smiles/icon_sad.gif ) for example – when overtaking a tractor with a long trailer, I used to be able to tap the accelerator, it would change down and power forward....not now. I have to change down manually and then it would take time to think about it before taking the command. This lack of power is particularly noticeable very on long inclines. Is there anything I could consider doing to bring back some of the original vigour? Or is this all I can expect. Andrew Kennedy