Okay, here's one of my bug-bears which I've never really got around to solving.

Here in 240V mains land (it's actually sitting at 247V right now), any of the smaller tubes, most notably F8T5s, F15T8s, F18T8s and F20T12s have an annoying tendency of instant-starting on magnetic gear.  The F8s and F20s being the worst culprits by a long way.  Don't think any of the Philips F20s I have in fact has ever NOT instant started now that I think about it.

Given that I've got a heap of Coughtrie SFB16s each needing a pair of new starters, I'd like to get some which are actually likely to do their jobs. 

I'd rather steer clear of electronic ones in this case as I need quite a few and those things are expensive.  Plus they look so boring!  If I was using a rare lamp, yes then I'd use an electronic starter - for general use though, especially when you're taking about garden variety current 8W, 15W and 18W tubes just doesn't seem worth it.  I'd rather have the blinking.

So - anyone got any suggestions for starters which are likely to actually work for the lower wattages?

I think that this instant starting of the 8W T5, 15W T8 and 20W T12, is probably caused by the lamps that strikes directly from the 240V mains. This is common in generic PL-L lamps in Israel, and was also happened in Tungsram T12 lamps in the past.
18W T8 only rarely strikes directly from the mains, because of its higher starting voltage.
It is also possible that the starter rating that are used is wrong.
These lamps needs a 4-18W starter. Electronic ones are better, because they usually preheats the electrodes as soon as power is applied, thus preventing the lamp from starting directly from the mains (This is also true with thermal starters).

Try FS-2/S2/ST151 (the ones meant for series 2x 18W on 36W choke). They work ok for 1 lamp as well

Thanks folks.  I've got a couple of Philips S2 starters here, and they do seem to work better - though even then it's hit and miss.

Finally managed to track down some electronic starters, eventually having to resort to buying them online as nowhere locally seems to have them, that's including electrical wholesalers in addition to the big domestic DIY stores.  Is the sort of thing I really prefer to just walk into a shop and buy to be honest.

Was surprised to discover a working starter in one of the SFB16s though - it's a bit sluggish and a bit temperamental, but does still work, and makes a very loud "ping" when opening.  Not bad after 44 years service...

When these lamps are operated in series pairs on a single ballast choke (the same as for the single lamp), they would never instant start...

Seem to have got a 90% effective solution here now with a couple of Arlan pulsestarters.  Still seems to manage to strike one lamp now and then before the starter has time to react - though the starter sockets aren't 100% so that might be the cause.

Series wiring would of course sort it - but these are individual ballasts, so not really an option without significant mods to the unit.