<initial sketch>
Same single-seat constituencies as now
Same voting form, but used slightly differently
Manual count as now, but with some simple extra steps if there is no majority winner.
All in all, a no brainer for immediate implementation, given
o the current highly undemocratic FPTP
o the time and effort it will take to implement any other plausible replacement for FPTP
o the total compatibility of PV with the two most likely alternatives (STV and AMS), and hence the suitability of PV as a first step towards either of them.