I moved to a village on the outskirts of Grantham a few years from South London a few years back.
Heres what I find
Good
Train links - not only to London , Grantham is on the East Cost line, so you have direct links to Leeds ,Newcastle , Edinburgh for that weekend away.
Schools very high ofsted rating for most and Primary schools class sizes are below the average.
I would say if you do the trip a couple of days to London , you will be fine , if you have to do it every day , it might grind on you.
Attractions on the doorstep - Belton House and Gardens, Belviour castle, Grimsthorpe Castle, TwinLakes , Woolsthorpe manner.
House Prices
Probably what attracts most people from outside the area in the first place, you dont need me to tell you what extra size and space you get for your money.
Country Pubs - So many nice pubs just a short drive away.
Potential
Town center very recently when a 2 million make over on its market square - while it can argued whether it was the best use of public funds, it does show that there is an appetite to improve it . Theres going to be a fine dining restaurant next year and theres already new nice cinema built a couple of years back and the town is attracting some shops that traditionally wont have come eg just last week an artist opened a shop - some links below.
Chef who worked under Gordon Ramsay reveals name of high end restaurant coming to Grantham town centre - Lincolnshire Live
www.lincsonline.co.uk/grantham/news/i-want-the-new-shop-to-be-a-place-where-local-makers-can-fe-9392491/
Westgate Bakery owned by Michelin star chef Adebola Adeshina opens in Grantham (lincsonline.co.uk)
Otherwise the town center itself is very average , not terrible but not great. Some good cafes , bakerys , restaurants. You can argue improving and I personally dont think the shops I mentioned wouldnt open if they didnt feel the same. You really need to walk around it and judge for yourself. Personally I drive 30 minutes to stamford if I want a shopping day out.
But the town center isnt its selling point , if the town center was perfect you would be looking at much higher house prices. How much time with Kids do you spend in a town center anyway- i personally prefer the outdoors and bigger hosue space these days.
More potential coming in the way of an designer outlet . Although that has stalled and cant promise that will ever happen , but various sources suggest it will. You will have to do you own research.
Grantham Designer Outlet Village (granthamoutlet.co.uk)
Also the East midlands mainline is getting a huge upgrade. If that all works out you will get more reliable trains and with in Cab signaling tech , dare I say it 35 min trains to london by 2029 as they can reach speeds of 125 mph.
A £1 billion railway upgrade between King’s Cross to Grantham (ianvisits.co.uk)
So the last 2 mentioned are planned - so you cant make a decision on that as I cant say 100% they will happen, but if they do house prices are only going up,
Crime -
I lived in South London , so my perception of Crime is a bit different to maybe some others, but if you read about a bit of shoplifting in shops in the local paper rather than stabbings etc. probably like most areas you get better and worse areas. Earlsfield as mentioned in another post is a council estate area and suffers from crime so Id personally avoid buying there . That sounds very snobby , sorry . Do some research it no worse than everywhere else.
Funnily enough when I moved to Grantham , i looked at Gloucester road and thats a good area , I would also look at one of the surrounding villages, Denton, Barrowby, Harlaxton, Great Gonerby as they are nice areas.
Like any areas theres good and bads but i would say its value for money and I personally like it. Everyone is different so please dont have your mind made up by a forum , you have go up and spend a few days there and paint your own picture.
Good Luck