Engine Keeps Cutting Out

I have an '03 TD5 - it's done about 80,000 miles and is beginning to have a few problems -

- the most irksome of which is that it keeps cutting out at inconvenient moments like when doing 85ish in the fast lane.

There is no real pattern - it can go for days without doing it - but it does seem to happen when you hit rougher road surface at that speed.

Any ideas much appreciated.

sounds like it could be a bas connection (supply or earth) to the fuel pump. Check them. It could more simpler be a bad battery connection.
Loius