Was your old boiler a non-combi?
Modern condensing combis I think are designed to be more complex and not last as long. I'm not sure all the complexity and fancy modulation etc is really worth it myself. I'd rather have a boiler that lasts 20 years and that any half-competent gas engineer can fix with a spanner and some spare parts.
£20k, jesus!
Condensing boilers became mandatory in UK just over 20 years ago
Whatever about a combi, you probably don't want a non-condensing boiler these days, not with gas the price that it is.
What's the cost savings? Also factoring more expensive purchase, repairs, replacements etc
Ye olde non-condensing boiler is usually about 70% efficient (that is, 70% of the heat from burning the gas goes into your house vs out the exhaust), sometimes worse (60% wouldn't be that out there for old ones). A condensing boiler, _if set up correctly_, will do 90% (95% for the newest models, allegedly). Now, the catch is that it'll only hit 90% if the return water is within a fairly narrow temperature range, so some system balancing is required, and in practice a lot of them end up more like 80%. But given how expensive gas is these days (at least in Europe) that 10-20% saving will handily pay for the cost of the boiler.
Old and new both condensing and both non-combi.