Thanks everyone for your perspectives. I also feel guilty for DH, I understand his love of Cornwall, but I guess I didn't really explain my perspectives too well, how much of a toll this is having on my mental health and the area we are considering.
My parents are the main reason for moving, if they weren't around, I don't think I'd feel this strongly, but I also feel cut off down here from everyone and everything. I have closer friends near to where we're thinking of moving to. I understand about building your own village and I've been attending baby groups, have some friends/acquaintances from work (we're both NHS workers so we can work pretty much anywhere in the UK, someone mentioned this), but finding it hard to build a village and obviously it takes years to build up the close connections that I'm needing at the moment; nothing beats seeing yours and your friend's little ones, who you've known since you were four, from playing together or rocking up at your mum's for a nap or home cooked meal without guilt. I'm missing out on seeing friends e.g. one of my best friends who lives abroad came to the UK for work, but I couldn't make it to see her because of having travel commitments already to see family 2 weekends in a row after that - I didn't feel the travel was fair on my LO & she didn't have the time to make an extra trip down to Cornwall. I know these are just one off events, but I feel similar things are happening frequently. We often travel to Bristol half way, so a 2/3 hour trip doesn't feel very long anymore. My partner has also struggled to make friends, so his only pull to Cornwall is the beaches/countryside really.
Regarding making the travel easier, flights cost too much and are not year round (I'm talking £600+) and the train is usually around £180-200, but I've taken the train a few times...it takes around 8 hours altogether.
The area we are looking at is the Peak district, which would be 1-1.5 hours from my family. This was somewhere my DH suggested; I hadn't suggested it initially as I was looking at somewhere a bit closer to his family too in London but, although he gets on with his family, I think I enjoy more about seeing them that he does. 1-1.5 hrs may still sound like a distance to some people, but compared to what we have now it is easy, we often travel for an hour to see work friends down here. I wouldn't expect my DH to move to where my parents live because it wouldn't suit our outdoorsy lifestyle, wouldn't be somewhere I'd want to bring up our child and I know my DH wouldn't be happy there. But the peak district essentially offers everything we have here, minus the beaches (although plus the mountains). We enjoyed climbing pre-baby, love walking/hiking etc, so I think the Peaks would suit us perfectly and he also said that he really likes it, but doesn't want to risk what we have down here.
Both mine and his family are incredible, I feel very lucky to have them both..they help as much as they can from a distance and I know they'd adore to see our LO more often. I feel we should make the most of them. My dad is 70+ and finding the travel increasingly difficult (he's always been an anxious traveller), so I feel the frequent-ish visits are time-limited (we basically aim to see eachother every 6-8 weeks either here, there or halfway but it's tough and we also do the same with my partner's family). My mum is also feeling the strain of being so far away from us&frequently gets upset. But they can't, and I wouldn't expect them to, leave all our other family behind, especially my Grandma who my mum provides a lot of support for.
I honestly wish I felt differently. Of course I hope that a temporary move would become long term, it would be more of a trial to make sure my DH was happy and I understand the financial strain and stress of relocating and we have spoken about this. I would absolutely not want to move twice in a short space of time, but is it more important to safeguard my mental health, or the money?