The summary of the information the nurse gave me is below (sorry if it’s long it’s 12 pages here!]
Folic acid should be taken ideally at least 1 month before ttc even if you have a good diet. It can also be found in spinach, broccoli, sprouts, green beans and potatoes. It says that if you have a higher risk of having a child with a spinal cord problem you may need a higher does. It does include in the list BMI of 30+, sickle cell anemia, medication for epilepsy, coeliac disease or diabetes so if in doubt speak to your gp!
Vit D - needed for growth. Recommended for all pregnant women and breastfeeding women. Oily fish, eggs, meat and some fortified margarine and breakfast cereal have vit d.
Alcohol, smoking and drugs is a pretty standard no, no and no where possible
Overweight and obesity - encourage to lose weight as can be higher risk and the ideal BMI is 18.5- 24.9 in preparation
Healthy balance diet - same guidance as nhs would give everyone. One third of most meals should be starch based such as bread, cereals, rice, pasta, potatoes but opt for wholewheat where possible. Eat fruit and vegetables and some protein each day fr9m sources such as pulses, chicken, fish. Try to include foods with plenty of iron, calcium, folic acid as the baby will need nutrients from day 1.
Iron- found in red meat, pulses, dried fruit, green veg, fortified cereal
Calcium- milk, cheese, yoghurt (low fat usually has the same amount of calcium as regular)
Supplements- recommended folic acid and vit d as mentioned before but also consider iodine. It helps the development of the brain of the fetus. You need more than usual when pregnant and can come from milk, yoghurt, eggs and fish. Some salt also contains iodine but go careful with quantities of salt. So one worth considering if you don’t think you get enough from your diet.
Fish - in general is good for protein and nutrients. Aim to eat 2 portions per week (this I struggle with!) but be careful which fish as some have high mercury. Bad fish includes shark, marlin or swordfish and tuna should be limited to 3/4 tins a week 140g per can or two fresh tuna steaks 140g cooked or 170g raw. Do not eat raw fish or uncooked shellfish. You should have more than 2 portions of the following as they can contain chemicals from pollution ; oily fish including mackerel, sardines, salmon, trout and fresh tuna. Sea bream, sea bass, turbot, halibut, rock salmon or brown crab meat.
Avoid lots of vit A as large amounts can harm an unborn baby. Liver including liver pate and cod liver oil suppliments and any suppliments with vit A should be avoided.
listeria can cause miscarriage, still birth and infections so avoid undercooked meat and eggs (yolk should be solid and be cautious with mayo and mousse etc which may have raw egg), module ripened cheese such as camembert, Brie and blue Veined cheese (hard cheese and processed cottage cheese are safe), pates including veggie ones, raw or smoked fish, unpasteurised milk (goats cheese and milk is usually unpasteurised)
Caffeine - limit this to a maximum of 300mg a day (tragically this can be found in chocolate 
)a rough guide says one mug instant coffee has 100 mg, brewed 140mg, tea 75 mg, 50g plain choc 50mg (milk choc has about half hooray) one can cola or energy drink 40mg
Stay clear of lambing season and cat poo if you suspect your pregnant and wash your hands after touching your feline friends
There is a bit about prescriptions but the overall advice is talk to your go before ttc.
The other recommendations are wear gloves when gardening to avoid some of the nasty germs that wouldn’t usually harm you but could a fetus. Wash salads and veg in case of contact with any cats, be extra vigilant on food poisoning, consider chicken pox vaccine if you haven’t had chicken pox before and consider hep b if you feel your at any risk. It recommends having your smear done before ttc if your due one as you can’t have one for 3 months after baby is born. See a doctor if you are in medication and consider your work environment. Gentle excercise is encouraged but if your planning a marathon or weight lifting speak to a professional! I hope some of this is useful. I was encouraged to change my diet accordingly so it became the norm before ttc and I have got better with the exception of fish which I’m not so keen on!