Hi Sandy,
In relation to Lancaster and Lancashire, some American sites seem to be mixed up on this. Lancashire is the County and Lancaster is the County town, I've seen it called lancastershire which is wrong.

St Helens and Prescot are adjoining towns, whilst living in St Helens for local goverment , you still could be under the civil registration authority for Prescot, being that some of the boundarys run close together.

If you have any more queries in relation to Prescot get in touch , I have the parish registers for that area, depending on which date you require

regards James Riding