Interesting that before the electrification to Ellesmere Port the line to Helsby had an hourly service off peak and half hourly in the peak. When the electric trains only ran as far as Rock Ferry there was an hourly DMU to Chester with a connection at Hooton, but on Saturday it was a through service to Rock Ferry, i.e. Rock Ferry to Hooton was half hourly on Saturday. Football? Shopping? When the electrification extended to Hooton there was a DMU from Helsby to Chester, reversing at Hooton, again up to half hourly in the peaks. If it could drop to four daily the previous service must have been for operational reasons, unless there's some traffic flow that has now stopped, like the Stockport - Stalybridge line.
I have a 1972-3 London Midland Region timetable which shows a half-hourly service between Rock Ferry and Hooton for most of the day, alternating between Chester and Helsby. There are a couple of peak semi-fasts in both directions and a couple of through trains to Llandudno, suggesting a regular traffic to and from North Wales. The weekday evening peak departures from Rock Ferry are a little odd though:
1618 Helsby
1628 Bromborough
1638 Llandudno (nicely timed for shopping in Liverpool?)
1658 Helsby
1708 Bromborough
1718 Chester (semi-fast calling Port Sunlight, Bromborough, Hooton and Upton-by-Chester)
1728 Helsby
1748 Chester (semi-fast calling Bromborough, Hooton and Upton-by-Chester)
1758 Chester all stations
1818 Chester all stations
1838 Helsby and a return to half-hourly service for the rest of the evening.
Leaving Hooton northbound over a similar period we have:
1636 ex Helsby
1652 ex Stanlow (not calling at Spital)
1658 ex Chester
1719 ex Helsby
1733 ex Chester
1801 ex Helsby (not calling at Spital, Port Sunlight or Bebington)
1808 ex Chester
1833 ex Helsby (terminates)
1843 ex Chester and back to half-hourly thereafter
The skipped stops in the northbound trains from Helsby seem to be for pathing reasons as much as anything else; from what I remember at the time, Rock Ferry was operated as two two-platform termini facing in opposite directions at the time so there was no capacity for a third unit to lay over. A lot of the passenger traffic will have been generated by shift changes at Stanlow and also Lever Brothers at Port Sunlight, so the Bromborough short workings may have been to accommodate Port Sunlight workers as well as providing extra capacity to the last large settlement within Merseyside. I suspect that electrifying to Ellesmere Port may have had its bottom line covered by regeneration funding.
As far as the Borderlands Line is concerned, remember that until circa 1980 the northern terminus was either Birkenhead North (where there was a third platform face to accommodate the connection) or New Brighton. Bidston was adopted as the terminus to keep the DMUs off a congested section of track (at the time there was freight to and from Birkenhead Docks using the section, and any shunting at Birkenhead North can also take up space on the running lines).
Electrification to Kirkby was a precursor to the closure of Liverpool Exchange- the mooted alternative for Bolton-Wigan-Liverpool trains was to have the DMU service terminate at Sandhills, i.e. one station short of the city centre and not really ideal on a layout with no room for a layover siding, so the terminating DMU would have to empty and reverse in between Southport and Ormskirk services. I'd agree that the natural end for that service is the bay at Wigan Wallgate, but the difficulty seems to be getting Merseytravel, Lancashire and TfGM to agree at the same time.