Many thanks for all the prompt comments, which are very helpful except that some people recommend switching to LED, some XENON, some say either of these could fail the MOT, others not. Guess I'll go to my MOT people & ask them before I go ahead. But a VERY useful exercise anyway. No need for anybody else to contribute as I now have a full range of opinions to digest.
The one thing I won't do is buy OEM - it'll have to be a main brand : Phillips, Osram or Bosch, because when I went into Halfords today for something else, they said although they won't be beaten on price (shades of erstwhile John Lewis?), their prices / products are the same online as in store, but they clearly aren't! shows it does pay to do thorough research, IF you've got the time of course!!!