I would go fixed (Disclaimer, I did fix for 10 years in 2016 @ 2.98%). With that in mind i don't regret it one bit. I'm in control and have had 6 years hassle free, not worrying about rates, changing etc. With rates at such lows it just seems like a no brainer to me. I could get a deal now at 2.19% under the same circumstances but that would save only £21 a month on a £578 monthly outgoing. If rates have no where to go but up, then 2.19% is a bargain. With your LTV and borrow amount it seems this % is available too.
But for how many months would you save that £21 for? Any how much extra capital and reduce interest savings would you make because of it. Taking a monthly repayment impact view on rates is impossible to actually value the true saving/cost.
Im currently looking to borrow more for an extension at the same time as switching my current deal on to a 10 year fixed and evaluating if the ERC charges will be beneficial against a theoretically stressed mortgage where rates go up only 0.75% more within the next year.
For me switching now and taking the ERC charges vs waiting a year and being impacted by theoretical 0.75% rise works out cheaper over 10 years. However if rates rise more than 0.75%, I save £150 ish per 0.25% rise. The risk is if rates remain at similar levels as now then obviously it costs me more, again by a similar amount to what it would cost, obviously.
Worst case scenario rates remain at record lows even through inflation rises and its cost me £10k over 10 years, even then i know exactly where im at for 10 years.