EBF DS refusing formula and i go back to work in 2 weeks - help!

[BadHairFatFeet]

My DS is 6 months this week and I go back to work in a fortnight.
After a rocky start to BFing (he had tongue tie) we got the hang of it and he's been EBF on demand ever since.
On the advice of my midwife we also introduced a bottle of breastmilk within 4 weeks so he does (grudgingly) take a bottle whenever I've been away from him for a few hours.
Before Christmas we tried to introduce formula to him over the course of 3 separate evenings. It was spectacularly unsuccessful! At a weighing-in clinic the HV told me to not worry about formula for now but try two weeks before i go back to work.

Still no success. We've tried Aptamil, Cow and Gate and are currently trying HIPP. I've tried a sippy cup, a free-flow sippy cup, his normal Avent bottle and a Tommee Tippee bottle. My husband has tried, I've tried, other family members have tried. He won't take it. Not only will he not take it but as we're currently trying to get him on solids, he's no refusing to take ANYTHING from me.

Should put solids on the back-burner for now and just focus on formula?
Has anyone else been in a similar situation but got it on track eventually?

N.b. If needs must I'll try to express as much as I can, but a) the letdown i get with my pump isn't half as efficient as it is with DS so takes me a while to get a decent amount.

Probably very naive but can you express milk instead of using formula at all? And continue with introducing purées in the meantime?

I would still keep offering the solids at this stage. Even if he doesn't eat tonnes it will get him used to family mealtimes.

Will he take ebm? If so, could you introduce the formula one ounce at a time? So if he takes 4 floz of ebm give him 3 with 1 floz of formula and keep it like that for a while and then add another ounce.

I'm afraid you've been given pretty poor advice by your HV too. I think you're probably best calling one of the BFing Helplines about how you can reduce your chance of mastitis when you go back. Sudden switching from BFing every feed to all formula isn't usually advised.

Are you using a hospital grade/ too knot head pump. Would definitely do as suggested and mix in half oz, then 1 0z and just keep slightly increasing the proportion of formula to Ebm.
Definitely keep going with solids and mix in a little ebm there too so you know he’s getting milk from different sources if he’s fussy about the odd bottle you will worry less.

Meant top knotch pump!!