Where to look for lectureships in mathematics in the UK?

Question

I am currently halfway into a 3-year postdoc position in mathematics in the US, and I have a good publication record (two papers in top general mathematics journals, one alone, one with a senior coauthor; another preprint, at least as good as these publications, with a different senior coauthor; several other publications in good-but-not-top journals).

I would like to pursue an academic career in the UK. I am only looking for jobs roughly equivalent to the tenure-track level (e.g., departmental lectureships, but I'm open to other options if they exist). In other words, I would like to get on the lecturer-senior lecturer-reader-professor track (or equivalent). I would like to try both Cambridge/Oxford and other universities in the UK.

I have been looking for lectureship job ads, but have found very few of them. I feel like I'm missing something. I've been looking in jobs.ac.uk and in departmental websites.

1. When? Are mathematics lectureships in the UK generally advertised year-round or mostly in certain months?
2. Where? Where are they advertised?
3. How many jobs? Do departments usually take at least one new lecturer per year?
4. Cold emailing? In departments where no job is advertised, is it worthwhile to contact professors in my subfield and heads of departments to express my interest in a lectureship?
5. External fellowships? Is it common to get on the lecturer-senior lecturer-reader-professor ladder by starting with an external fellowship? What, if any, are the relevant fellowships?
6. Oxbridge different?: Are the answers to the questions above different between Oxford/Cambridge and the other UK universities?

I understand that the recent COVID-19 situation added uncertainty to the process. I am interested to know how things were before the pandemic, and if you have concrete information - how they are now.

Answer 1

Just to turn what Daniel Hatton said into an answer. Note that the following answers apply to UK academia generally, but I've no reason to believe they differ for mathematics:

1. Jobs are advertised at whatever point the department manages to secure approval to hire from their school/faculty.

2. Everything will be on jobs.ac.uk. Some things might also be advertised in the Times Higher Education, NatureJobs and on the departmental website. But everything will also be on jobs.ac.uk

3. Very much depends on whether the department is expanding or contracting, what student numbers have looked like in recent years etc, but in general, I'd assume department hire one person for every person that leaves. Actually at the moment many departments arn't even doing that - we've hired one person in four years, but had 8 people leave.

4. If you do this, the answer will be to look for fellowships (see below)

5. Yes, one common way into the Lecturer, Senior Lecturer, Professor path is via an externally funded fellowship. These do vary field to field. You should at look at the EPSRC, the Royal society, UKRI future leaders fellowships. There are likely also things specifically for the maths field I don't know about.

6. All of this is more or less the same at OxBridge, although there you might find that the colleges may also fund research fellowships themselves occasionally. Again, these will be advertised.