For the OP: if you have any problem with the seatbelts, after you've replaced them with an aftermarket set (such as throwing a code, related to the seatbelts), I expect Lotus will void any warranty.
I've checked into how to do replacements:
1. Locally for me, NO ONE was interested in doing this job...unless I purchased OEM belts from factory plus the mechanisms that go along with the over-all assembly. No one wanted to risk (for example) installing an aftermarket webbing which could fail, in the event of a high-speed collision, or re-using the original mechanisms, even though they're still next-to-new (about 4,000 km on the car). They were all too worried about being sued.
2. The choice made by several other Forum members, was to remove the OEM assembly, complete with the OEM belts, then ship that off to a company who replaces the webbing, using their own webbing...which is usually all one color (yellow/red/blue/etc.).
3. Some in the UK have used Hide & Seam Automotive Interiors which judging by all the ++ testimonials of Forum members, looks to do great work...however for a price which matches the quality of their work.
4. For me, I wanted something different so instead of a one color replacement webbing (ie. all red to match my Vivid Red exterior), I purchased replacement webbing from AliExpress, that's multi-colored: black with dual red stripes in the middle. I'm stuck doing the replacement myself, given this type of webbing (ie. I can't send it out for one of these companies to install; it's not their own webbing). Like others have said, many OEM webbings are made in China...so I'm satisfied this webbing is strong enough. I've also watched several YouTube videos, showing how to replace webbing, so I've some idea how to do this and will use the Emira shop/service manual pages for additional guidance, plus several postings made by other members who've done this. I'm fortunate that my spouse has both a serger and sewing machine, and she's graciously volunteered to sew the replacement webbing into place on the retraction mechanism, when the time comes. I'm now in the process of adding speakers and sound insulation, so it'll be awhile before I tackle the seatbelt job.
Hope this helps some, who are contemplating replacing seatbelts. It looks to be a somewhat challenging and time-consuming job, but doable. Moreso if you're like me and already removing seats and other paneling, for speaker or sound deadening work.