Hi. Like yourself I (and my wife) are classed as 'vulnerable' as we both have differing heart conditions and she is mixed race. The guidance for fishing is now quite simple. Yes it is ok to go fishing. Angling clubs have imposed their own rules in order to open safely to their members, so it would be worth checking with any clubs you may be associated with. Added rules apply to night fishing for many clubs too.
The Angling Trust have some good information if you have not seen it
https://joinanglingtrust.net/angling-support-hub-phase-one/
Although we are all allowed to go out and fish, we need to abide by rules in place and make sure to look after ourselves and others by keeping to social distancing rules, washing hands, not touching metal gates and railings where possible and being aware of any symptoms.