Solar Street Lights can be effective, even in Ireland.  VeeLite typically design systems that will operate at full lighting output for 2 hours each night. This can then be extended to operation for the whole night, even in December and January, by adding motion sensor control.  These allow switching to full light output only for a pre-set delay, usually between 1 and 5 minutes, before switching back to a low output or switching off fully.    In Summer, there is no shortage of solar energy and the hours of darkness are reduced, so all night operation may be possible at full output, or longer lighting delays or higher light levels, etc are possible.  An alternative setting is for higher light levels from sunset to say 10pm, 11pm or midnight etc and switch off (or minimimal light activation) after this.

From this, it is important to analysis the lighting needs before deciding on the system.  How much light is required, for how long, between what times each night, is it seasonal, etc.  Is there any electricity supply nearby ?  If so, it usually does not make financial sense to install Solar lighting, as the Capital cost is typically 4 times higher.