You can pick up a cheap VHF for about 50 quid. It won't be amazing (typically the waterproofing is a little suspect - but put it in a dry bag and it will probably do you fine). A well respected brand like Standard Horizon will do an entry level model for around £100 if you shop around. Unlike flares though they will let you:
(1) Tell the CG you have a problem but don't need a helicopter, two lifeboats and every other vessel in the area to rush to your aid.
(2) Get weather, safety or other advice from the CG - just be listening in.
(3) Tell the CG you are running late but don't need help so no need to initiate a search if a shore contact calls it in.
(4) Give the CG a location to zero in on (which Mobile can't do - ignore what you see on telly - triangulating a mobile signal is not practical in most rescue situations). With VHF the CG's can find your direction, and a lifeboat or helo can pinpoint you.
(5) Call a passing vessel to ask for a tow if you have a breakdown.
(6) Give you the knowledge that help IS on its way. Many a person got into more difficulty after their first attempt at calling for help, when if they had just stayed where they were help would have got there quicker.
A VHF course and certificate is usually about £100. If you hunt you may find a local sailing club or night school doing it for a good bit less. However, whilst it is legally required for non-distress use, and certainly makes sense - I don't think you will find anyone on here who would recommend NOT buying a VHF and carrying it anyway, even without the certificate.