I live about 10 miles from Formby and my only thoughts are :- a few pubs on S4S / a couple of laybys on the A565 (noisy) / Formby Tesco but that's about it. We occasionally have wild campers on the beach approach in Southport but the slope is very steep and I wouldn't stay there Your best bet could be
https://southportpleasureland.searchbreaks.com/ (£15pn) It is 15 min walk to Southport town centre and 5 mins walk to beach / swimming pool / supermarket. Buses and local train to Formby & Liverpool. about £15 pn