The only (almost) universal database of UK names and addresses is the full electoral register. It shows the names and addresses of everyone who is registered to vote. (So, for example, it won't show people with no right to vote in this country or people who, for whatever reason, have decided not to fulfil their legal obligation to register. Neither will it show minors).
Data protection laws mean that the ONLY people who can access the full electoral roll in its electronic form are the police, the security services and certain specific bodies such as credit reference agencies. The electronic version is NOT available to the general public.
The only way that 'Joe Bloggs' can view the full electoral roll is to go to the relevant council office in order to consult the paper version. That's organised first by electoral wards and then by street names. (i.e. there is NO alphabetical index of voters; you have to trawl through the entire list, street by street, to try to find the person that you're seeking).
Further, there are strict rules which govern the way in which you can consult the full register. The following is taken from my local council's website but will apply across the whole of the country:
"The full version of the register contains the details of every registered elector. Access to this register is restricted by law and the use of the data is limited to certain purposes.
A paper copy of this version is held in by the Electoral Services Team at the Council offices. This may be inspected, under supervision by a council officer, by any person during usual office hours (subject to satisfying the Electoral Registration Officer as to the necessity of seeing the full information rather than using the open version of the register). You must make an appointment to view this register in order to ensure that there is someone available to supervise your viewing. Please contact Electoral Services on 01449 724678 to make an appointment.
Handwritten notes are not permitted. The use of copying machines, photography and computers is not permitted. This includes entering data into a mobile phone or electronic device.
There are restrictions on what information obtained from the full register can be used for. You will be required to complete and sign a declaration form prior to viewing".
As well as the full register, there's also the 'open' (or 'edited') register. That shows the name and address of every voter who has NOT ticked the box on the electoral registration form inviting him/her to be excluded from that register. The open register is available for sale (for many thousands of pounds) to organisations such as direct mailing companies. So a large number of voters (probably the majority) DO tick the box which ensures that their details aren't on the open register (in order to avoid getting loads of junk mail).
The open register is also purchased (for a vast amount of money) by 192.com, which is the ONLY firm to do so. They then make their profit by charging people to search it online. So, contrary to what you wrote in your post, 192.com is entirely 'legit'. However
(a) as you've found, they're far from cheap ; and
(b) many voters (possibly the majority) won't be included in 192.com's database because they've only got the open register to work from, not the full one.
Other than either using 192.com (and hoping that the person you're seeking didn't tick the box to exclude their details from the open register) or spending hours wading through the paper version of the full register under the supervision of a council employee, there is NO simple way of tracking someone down. As has been suggested, you could try Facebook or even a simple Google search (which often finds people who are, for example, the secretaries of local community groups) or if, say, you're trying to track down a long-lost relative, you might try a letter to the local newspaper.