@Linbers Are you saying that these disconnections ONLY affect wifi connected devices? No such problem with ethernet connected PCs, Macs, etc?
Whether you use an ordinary 'phone is neither here nor there for you still have the 'phone line. You can buy a cheapo corded telephone from Ar**s for less than £7 to carry out the test as suggested by @Keith_Beddoe
Hi all, thanks for all your help and suggestions and sorry for taking so long to reply. Just to update you I have replaced the modem/router with a TP Link one, and all of the problems that I was experiencing have gone away, no connection drop outs and all working well