Good luck - hope you find somewhere.
If you’re prepared to sign a 6 month or year tenancy I think you should be able to get somewhere.
Most LLs don’t want to offer a longer tenancy to start with, because getting nuisance tenants out is just so much harder if they do. Most will go for a 6 month tenancy to start with, but the understanding often is that it will continue on...but that’s not binding on the LL or the tenant. LLs often say they are up for a long let, but will start with a 6 month tenancy and then it’s them who send notice and end it at 6 months because they want to sell or whatever.
The thing is, LLs and tenants can never be certain how long the other person wants to be in the agreement for. You can ask, but no-one is committed for longer than the legal agreement and no-one has to remain in it longer.
They might well ask how long you expect to be around. You could equally ask them. It all means nothing, the term if the tenancy is what counts and gives you your minimum terms. You might need to sound positive about being a long term tenant. They still aren’t going to be offering you a minimum term of longer than 6 months or possibly a year as you could turn out to be nightmares and they will want you out. Obviously if they do suggest a longer term tenancy (totally unlikely to start with...much more likely after a first term has gone well) you couldn’t agree.
If you feel you have to be fully upfront about your position and future, then you might struggle in a competitive market where there are lots of people who want really long term rentals. However, LLs have to accept that tenants move on. If you look like decent people who will pay, you should be able to get somewhere.
It’s hard to imagine you could t get something if you’re happy to go with a standard tenancy agreement.