"Roland Perry" wrote in message
news
Cleaning would help, but they are older than you think. Introduced in
1995.

I'm sure they were introduced later than that. They were built in c.1995,
but my memory tells me they didn't start to enter service until 1997-8.

The WAGN units are just at the beginning of their first cycle of overhauls;
I don't know how this affects the South Eastern ones which had a certain
amount of "remedial" work done upon transfer (and are therefore generally in
a slightly better internal condition).