Replacement headlight now speedo affected ?

[travelbug]

Hi there, can anyone help me here. Reading around here there seems to be a hell of a lot of knowledge and wondered if anyone had any suggestions.
My mum has just had a new headlight fitted to her Yaris, now intermittantly the dash is saying the lights aren't on, now she says the speedo is going all over the place with strange speeds.
I haven't actually seen this for myself as unfortunately I'm 200 miles away, but she's really getting worried about it- I suppose you would when your nearly 80.
I suppose like any son I get a bit protective for my mum and don't want to just send her to a garage where she may get stitched up. Other than jumping on a plane to visit anyone got any suggestions as to the probable cause ?
Thanks in anticipation