Ref SIPPS - remember they are primarily designed for retirement income. You can invest into trusts/funds into them but they are much more rules around them than ISAs. For example taking money out is not simple unlike ISAs.
For a beginner I would start with ISAs. For a beginner or even moderate investor I would avoid Forexs and other such stuff, even with videos on You Tube.
Ref Hargreaves Lansdown - they did make a mistake recommending Woodford Equity for his last 2 to 3 years when his performance was clearly very poor. For 20 years he made money year after year when at Invesco turning £1k into £15k. No one can buy something and not check its performance say once a month. Also do you your checking don't rely on someone else's Wealth 50 etc. To be fair to HL they recommend 50 funds, Woodford Equity was 1 of 50.
Ref Vanguard funds - there is no harm in investing in them (at present) - they are tracker funds which means they invest in everything that is in an exchange (the Good, the Bad and the Ugly). Its a mathematical programme that does the picking with no value judgements which keep their costs down and so helps performance. They are massive funds too which keeps costs down. They are for people that want to invest and not check on performance very often. Because they invest in everything performance should follow the general index, no better, no worse.
I ran an Investment Club for a lot of years, but I don't invest in individual shares, but did for the club. It was partly fun, partly interest, partly social, partly to make money. Over 15 years (2001-2016) we had a return of about 8% per year against 1% for the FTSE 100. By grouping together and paying £50 per month per member we could buy a share every 8 weeks. I would bring 3 or 4 shares for consideration and the club said yes or no.
At the end we decided to close it down after our IT Excel expert said he had to leave to develop his own website (selling Split rail tickets) which had taken off. A lot of clubs started up around Dotcom years but folded within 5 years.
Shares we owned near the end were:
that were Bad for making us money - Vodafone, RBS, Oxford Biotech (now excellent after CV19), Lloyds
Good - Astrazeneca, ARM Holdings, JPM Russian Securities Trust, Legal and General, Greggs, Renishaw, Fresnillo, Berkeley Group.
So/So - BP, Balfour Beatty, Caledonia Trust.
We tried buying quality that was out of favour or had been treading water.