Small talk is the fuel that makes social encounters run smoothly. The British - who are resistant to intrusive questioning, prying remarks and direct interrogations - are very comfortable with small talk.
Completely safe topic areas are: the weather (inevitably); your route (though avoid becoming a motorway bore); your surroundings (admiring the garden, the view, the decor); general news (but keep it non-political); the wellbeing of mutual friends and acquaintances; children ( if you have any); sport (no boasting). Asking someone "How do you know [your host]?" is an acceptable ice-breaker, but asking 'What do you do?' can sometimes be seen as too direct and intrusive (a circumlocution such as "Do you work with xxxx?" is more acceptable).
Areas to be avoided are: age (it's considered rude to ask someone's age); appearance or weight (too personal, unless it's a generalised compliment - "you look well"); money (it's absolutely fatal to ask how much something cost or how much someone earns); relationships (could be seen as a pick-up); politics (too nosy); religion (potentially controversial); complaints, e.g. about the food, the seating etc. (offensive).
In general British conversation will run very smoothly if you avoid direct questions, and opt for oblique evasions and general comments. Once you've learned to decode small talk, you'll be surprised how revealing it is.