Having recently begun the pilgrimage which is T3 ownership, I have found that I am not entirely happy with the 4 speed box fitted to my 1.6TD It seems to be really happy cruising at 50mph and sadly I am struggling with the shame that is being overtaken by EVERYTHING on the roads

I have a few ideas and wondered what the general consensus was. Either changing the ratios of my box (never done it before...quite daunting) or swapping it for an alternative 4 speed with better ratio top gear or fitting a 5 speed, something which I am not insistent of as I just want to make it a bit easier on motorway cruising. As a novice at repairs and maintenance I would like to know what is the best value way to improve the situation
Many thanks