There is a mini housing boom going on at the moment, and a pandemic.
This means that it is a sellers market, so they have no need to sit around and wait for a bird in the bush - a buyer who has a house not yet on the market, let alone under offer, and also viewings are done under strict COVID safe protocols, in our area vendors leave the house and the EA does the viewing...no one will let you in if you are not a strong contender with a proceedable purchase.
There are still buyers rushing and hoping like mad to beat the SDLT holiday deadline...and you can't help with that so you aren't a strong buyer atm.
However. This will calm down over the next couple of months. It might calm down to the point where, if an EA recognises your own house as a likely quick sale, they will arrange viewings once your house is on the market.
If the market grinds to a near halt you might even be able to view whether or not your house is on the market. But in those circumstances the chance of you selling also goes down.
So you have to decide whether you are willing to put your money where your mouth is.
Does your search area have to be so very specific? I had some very definite search criteria...and am buying a house that is the opposite of one of them, because when I viewed it, it worked! This has happened to me once before when buying, too.
The mortgage idea is a good one, if you can borrow against your income and / or value of your existing house. But check what the costs would be, for getting the mortgage and then paying it off after a very short while.
If you own two houses for more than the specified amount of time you will pay the higher SDLT rate for the new house. If you buy while you still own your current house you will be charged it - but can claim it back if you then sell your first house within the allowed time . Look it up on .Gov.UK under stamp duty.
Things that make you a strong buyer:
Not being in a chain, or being in as short a chain as possible
Being a cash buyer
Buying from the proceeds of your current house without needing a mortgage
Letting it be known that you really want the house and will proceed efficiently and not mess them about.
So both approaches have pros in terms of presenting yourselves as credible proceedable buyers.
Also, once you are ready to go be pro-active. Sign up with lots of local EAs and tell them what you are looking for. They will then often tell you about a property before it has even arrived on Rightmove.