Leather care products are fine for keeping it in good condition. Mine is light in colour and no issues.
Limited use with no garage is possibly your biggest thinking point. Any car benefits from good storage and regular use. A neighbour has a TVR he keeps in a rented garage. He'll keep it on his drive more often in summer than winter to save going to the garage. An outdoor cover will ge an absolute minimum A car coccoon better. A rented/borrowed garage better still.
VED is high for 5 years, SORN can help a bit for extended storage but you can miss out on fine winter days for driving.
My advice is not to treat it as a "fine weather car" but use it. Join your local MMC centre. Go now before buying to get feedback from members there. I think Oxmog is your local.
I've done 7k+ miles in year 1 with my Plus Four inc a tour of Scotland. Similar to previous Morgans. Year 2 is likely to ge higher with two Scotland trips planned plus other stays away. The Plus Four is a good tourer with a case on the luggage rack plus stuff on the shelf. Performance and ride are great. One warranty fix for a minor behind the dash problem. I chose the auto so have the choice of auto or manual paddle shift.
A chunk of money to buy but absolutely no regrets.