Dear Annie, I have decided to share my thoughts on your situation and hireath, because you seem like a sensible person who can take ideas on board and decide how much they suit you.
I understand the concept of hireath very well, and would say that it one important factor. However, I have at some points in my life, taken a sensible decision rather than a heart-felt one. I have not regretted them because I acknowledged my heart's feelings, and said 'I am still going ahead with what seems most sensible now'.
Having acknowledged that and sought counselling, I would consider a stay in Lincolnshire. This assumes that the conversion would be done anyway, or that there is room for you to stay. I think you are in social housing - the usual time you can be away from a property is 3 months at a time. So you could go for a month, meet people in the community, find out about transport & community services, then go back to Wales and think again. You could try another month and see how contact works with your grand-daughters, knowing you can return to Wales.
I don't like to post about where I live, but the countryside where my family has been for generations, which holds my heart, and where I have been able to return, is much more like Lincolnshire! Work and family have taken me elsewhere, but I always found people to care for and to care for me, and places to cherish.
I know that you will make the right decision because you will make it work, whatever you decide.