If you are trying to design software that includes a Geographical element it is easier if you are working with data that makes some kind of sense.
The following are a list of sites where you can get good and consistent information on Local Authority Geographical Datasets within Scotland and in London. There has been an improvement in the quality and extent of information available but open data still remains patchy. Fortunately some datasets are available. The interesting thing about this data is that although it is rich it is largely unstructured and without relationships. Fortunately if there are geographical attributes then these can be used to spatialiy analyse the information and create relationships from which you can start to construct better systems.
I understand why the data is patchy. To really publish well it is a necessity to get your systems working well so that the export (and publication) of data can be at least semi-automated. Without this it is simply too onerous for staff to repeatedly perform Extraction Transformation and Load procedures on ever larger numbers of datasets. Taking a step back however therein may lie the benefit. The quicker they can learn to cleanly optimise and export and hopefully automate these procedures the more likely they are to have their systems working properly and importantly the more investigation and experimentation they can put into linking their datasets. The skills to link these datasets constantly to a web data portal being similar to the skills required to link between systems.
It might be expected therefore that better availability of open data is reflective of better internal systems.
Here is the information that I was able to identify through Google Searches at February 2018.
Angus Council Open Data Portal
Argyll and Bute Open Data Portal
Dundee City Open Data Portal
Moray Council Open Data Portal
North Ayrshire Open Data Portal
North Lanarkshire Open Data Portal
Perth and Kinross Open Data Portal
South Ayrshire Open Data Portal
and scheduled ancient monument information can be obtained here.
Here is London