I can do the application fine, it's just the payment that I can't do. Have tried clearing cache/history etc. and have tried on 3 PC's. Nothing works.

Eventually I used a US based commercial site and collected my e-visa very promptly but a quite a hefty premium. However it saved me the hastle of having to report to the visa-office here in London for a regular visa.
The US site was simplicity itself.

I ended up bouncing through a connection in Australia. Same credit card, same details, etc. and payment went through first time without any issue. All very odd.

I've seen various reports on TripAdvisor as well of using a company called Visa Genie to do it and they're not too badly priced (�65 all up I think).

Worked for me with MBNA AA UK card just a few days ago. Went through to 3D secure but nothing required and was approved. Before that tried with the Travelex Supercard and this failed.

keep using different credit cards.

It is nice that we can do this online but it is very expensive.

we are staying only a week in india and we have young toddler and paid almost $62 for each of us. India's neighbor Nepal don't charge fees for infants or toddlers.

On arrival passengers with e-Visas are directed to a separate location in the immigration hall. The line ahead of us was very short, maybe 10 people in all, but progress was disappointingly slow. They collect biometric data and the finger print registration screens were being difficult. One passenger in front of me took almost ten minutes to complete the finger print bit while the official leant acoss his counter over and over again to polish the screen. This was happening at several of the four or five counters open. When it was our turn we were not fingerprinted and I guess that this was because we had a 'proper' visa issued earlier in the year and the data collected then was still on record. For us the processing time was 1-2 minutes.

Doesn't mirror my experience on the 24th. Two separate queues, (oh why oh why - just have one!), I joined the shorter one and even with 4 people in front was out of there within a few minutes. Providing my biometrics was painless.

Reports suggest that getting an e-visa is still hit and miss but using 3G or 4G instead of Wi-Fi is a work-around that might do the trick. The fee may have come down too. That would make persisting more attractive, rather than just giving up and getting a regular visa.

Just a data point worked fine today using Natwest debit card

If I stated in eTV application that my intended airport of arrival in India is BOM. However, due to change of scheduling I arrived in DEL as my first point of entry in India. Will the immigration officials at DEL accept that and let me in without any trouble?

You can enter from any of the 16 designated entry airports, regardless of what you stated in your application.