Can Anyone "shed some light.."

I appreciate that this reply is not answering the question, but I find the reference to a "4 amp blade fuse" to be a bit concerning. Blade fuses are often intended for vehicle use at a nominal 12 or 24 volts with a limit of 32 volts, and are not suitable for mains voltage use.

However the improper use of SELV fuses on mains voltage would not stop the lamps from lighting.

A simple test WRT the actual fault, would be to use an old fashioned Drummond test lamp on the mains input to each bollard. If the lamp does NOT light then that suggests a fault in the cable, or in upstream joints or connections. Any chance of  buried joints in the SWA, that have failed open circuit?

If the test lamp DOES light then that suggests a fault in the lamp, the lamp holder, or the connections thereto. Badly made lamps that don't make contact with the lamp holder are a possibility, as are faulty lamp holders. I have seen porcelain lamp holders that permit of the lamp being inserted wrongly such that it fails to make contact.

And finally, are you CERTAIN that the non functioning bollards are on the same circuit as the one that functions.

Could they be on a different circuit ?

I wonder if by 'blade fuse' the OP is referring to 'NS' type fuses & not the low voltage car type fuses? NS fuses are HBC fuses & very much rated for use on the mains. 

I've used these, in suitable holders eg. the 'safeclip' range, to provide a more ... economical alternative to a Lucy style cutout.

I wonder if by 'blade fuse' the OP is referring to 'NS' type fuses & not the low voltage car type fuses? NS fuses are HBC fuses & very much rated for use on the mains. 

I've used these, in suitable holders eg. the 'safeclip' range, to provide a more ... economical alternative to a Lucy style cutout.

Yes they might well be NS types fuses, these are entirely suitable. However the term "blade fuse" is often used in reference to the vehicle fuses.

I think we need more info to be sure of what is there - if the OP is still stuck after making another visit, then taking some pictures and sharing them might help inform discussion.

(Yes I wondered about what was meant by  a 'blade' fuse i n this case , but no-one would use one of these on a mains design - would they ?
 
- I assumed a fuse holder with blades for round fuses. like a small one of these..)

To be fair, unless the main supply is shared with something really bosky say more than a 16A breaker, I'm not sure why each bollard needs its own fuse anyway.

Again a photo would probably avoid confusion.
Mike

Morning all,

Thanks for all your suggestions and input!

The long lead (it would need to be quite long!) Temporary supply is not a bad shout to verify whether a supply or at end of line issue 

The bollards are all on one circuit, -and as above, the oddness was due to them All having stable mains voltage present.

Nb, no funny car fuses or oddness, some bollards come with a small street lighting fuse in line, above the SWA gland plate and below terminals with internal cabling which supplies the lsmp holder.