Ferritin 34 (30 - 400) waiting for iron infusion for anaemia because I can't absorb iron tablets
Well, that's being dealt with but you can still help raise your level and keep it there by eating liver regularly.
Vitamin B12 247 (190 - 900) first B12 injection given June 2017, to take every 3 months and waiting to be booked in for next one
Did you have loading doses? Usually 6 over 3 weeks? Your injection was 5 months ago and you should have them every 3 months - chase them and make a nuisance of yourself, this is YOUR health they're messing about with.
Vitamin D total 35.1 (25 - 50 vitamin D deficiency supplementation is indicated) waiting on level of vit D to improve on 800iu. Been waiting since 2014 when level was 28.7
You should have had loading doses back in 2014 when your level was 28.7 - see NICE treatment summary for Vit D deficiency:
"Treat for Vitamin D deficiency if serum 25-hydroxyvitamin D (25[OH]D) levels are less than 30 nmol/L.
For the treatment of vitamin D deficiency, the recommended treatment is based on fixed loading doses of vitamin D (up to a total of about 300,000 international units [IU] given either as weekly or daily split doses, followed by lifelong maintenace treatment of about 800 IU a day. Higher doses of up to 2000IU a day, occasionally up to 4000 IU a day, may be used for certain groups of people, for example those with malabsorption disorders. Several treatment regims are available, including 50,000 IU once a week for 6 weeks (300,000 IU in total), 20,000 IU twice a week for 7 weeks (280,000 IU in total), or 4000 IU daily for 10 weeks (280,000 IU in total)."
800iu will never in the reign of pig's pudding raise your level. It's doubtful whether your GP will now raise your prescription dose, it's worth asking considering you should have had the loading doses 3 years ago, but to be honest D3 is very cheap you might just as well buy your own supplement, it will probably be better anyway.
The Vit D Council recommends a level of 100-150nmol/L.
My suggestion is to take the equivalent of the loading doses you should have had, that is 10,000iu D3 daily for 4 weeks (280,000iu) then reduce to 5000iu daily and retest 3 months after starting supplementing. Once you've reached the recommended level then you'll need a maintenance dose which may be 2000iu daily, it's trial and error so it's recommended to retest once or twice a year to keep within the recommended range. You can do this with a private fingerprick blood spot test with City Assays vitamindtest.org.uk/
Normally I would suggest D3 softgels but as you have Hashi's an oral spray is better absorbed. Take a look at BetterYou who do 3000iu and 1000iu doses. Start with the 3000iu dose and triple dose (so 9000iu daily) for 4 weeks then double dose (so 6000iu daily) until the 3 months is up then retest.
There are important cofactors needed when taking D3
D3 aids absorption of calcium from food and K2-MK7 directs the calcium to bones and teeth where it is needed and away from arteries and soft tissues where it can be deposited and cause problems.
D3 and K2 are fat soluble so should be taken with the fattiest meal of the day, D3 four hours away from thyroid meds.
Magnesium helps D3 to work and comes in different forms, check to see which would suit you best and as it's calming it's best taken in the evening, four hours away from thyroid meds
Check out the other cofactors too.
BetterYou do a D3/K2-MK7 combination spray which would save you buying a separate K2 supplement.
But before any of your nutrient levels can improve, you need to address the gut/absorption problems as mentioned.