Two of us went on the premise of a long weekend. We liked it so much we stayed on the trail for the whole week, and only returned home due to a prior appointment (which proved useless, drat). So we had clothes for three days and we did washing in the basin each evening. We had a small laptop, snacks, and not much else.
The South West Coast Path is dotted with B&Bs, inns, pubs with accommodation, etc. These are often placed at convenient distances apart, 10 or 20 km at most usually. Accommodation prices ranged from 50 GBP at a simple golf course (the room had no proper heat, but the lounge/restaurant was charming) to 95 GBP at the Tinners Arms in Zennor (population 217 as of this writing), a spotless room above a pub from the thirteenth century. The chef there was from afar and cooked spectacular food in this, the middle of nowhere.
You can camp instead, and in the high season you may even need to. We went in autumn when there were few distance walkers (downsides: not warm, some rain, quite a bit of mud in spots, every sleeping place in Porthcurno closed for the winter, but a B&B took us in and the local Elvis impersonator invited us to stay with him but he drove a camper van so...).