It's a question for your JISA provider. I suspect that unless they're a full-on stockbroker, the answer will be no though - it's likely to involve more effort for them than just buying shares on the open market.
The other question is why you'd want to buy the RM shares. Shares in an IPO are priced for the seller, not the buyer, and you don't have the natural balance shown on the open market. Expect a rapid change (positive or negative) immediately after launch as everything adjusts to what the market thinks Royal Mail is worth.
Personally, I'm not buying. I don't know much about postal logistics, I don't see any long term advantage the RM has over other post providers (although their unionised stance and unwillingness to adapt could well be a disadvantage), and it doesn't fit in well with the rest of my portfolio.
IPOs are generally under-priced evilkitten - simply because the underwriter doesn't want the risk of having to buy any remaining unsold shares.
Will speak to HL, the JISA provider. I don't want to buy the shares within the JISA as her allowance has already been used for this year. I just wondered if there were any age limits that actually applied in buying shares like these?
For public sales, generally they are. It would be an embarrassment to the government if people lost money immediately, and would be seen as a failure (despite the taxpayer benefitting). For a private sale, no. Last minute.com and Facebook spring to mind as a couple of high profile ones that have tanked.