Hi. I volunteer for a rabbit charity. This is the advise we give.
Rabbits should always be kept in pairs. Mixed sex pairs or spayed/neutered rabbits tend to work best, but same sex (still spayed/neutered) do work. Groups work also, but they are a bigger commitment and expense.
Rabbit rescues sometimes offer "bonding" to help find single rabbits a partner. It's basically speed dating for bunnies. Your rabbit spends a week or so at the rescue and returns with a "husbun" or "wifebun" (less catchy!). If you want to get a mate for him (and I strongly advise that you do) look to see if this is something offered where you live. It's horrible for owner and rabbit alike if a second rabbit is bought/adopted and constant fighting breaks out.
They should have unrestricted access to a minimum of 60sq ft of space 24/7. Letting them out of a smaller confined space at certain times of day isn't adequate. Think of it like a prisoner being given "yard time". Does an animal deserve only "yard time"? Indoor rabbits can be left in a decent sized room free range all day, but they will be destructive, even when kept in pairs and given plenty of toys/enrichment.
Personally, I have had house rabbits eat curtains, sofas, skirting, architrave, plasterboard, wooden furniture and electrical cables which we were certain were "bunny proofed". Do not underestimate how troublesome and mischievous they can be! It makes them wonderful pets, full of personality and quirks, but they are a big commitment; especially when kept indoors.
As mentioned by other posters, you cannot bring an outdoor rabbit indoors and so on. They develop their winter coat for the environment they are living in. If you then bring them into a heated house, they will overheat. An unheated converatory or garage in winter are your best bets, rather than a fully-heated family room. Similarly, you can't keep them indoors and then put them in the garden to reclaim your family space. For example, if your rabbit is in your dining room and you have people over for Christmas, you can't put the rabbit in a garden for the day, as it won't have built up the outdoor winter coat it needs. If you don't have the space for them indoors (or want the destruction) you can get lots of very good outdoor accomodation these days.
www.duchyfarmkennels.co.uk/shop/dog-kennels/the-birch-dog-kennel/ offer insulated accomodation. They are pricey but they deliver and build for you. This is what I have for my own rabbits.
As mentioned previously, Runaround are good also. Their tunnels are very good for getting the square footage into a smaller garden or awkward space. I have seen these damaged by foxes, however, so I'd recommend encasing the tunnels in predator-proof mesh if you suspect there may be a risk of foxes in your neighborhood. (Chicken wire is not predator proof.)
Finally, due to the cost of vaccinations, pellet feed, litter (if you litter train them; they are quick learners), hay and housing, plus time for cleaning, health checking and keeping entertained, I'd consider carefully whether you want a rabbit. They are the most neglected pet in the UK because people think they are easy to look after. Sadly, this is untrue. They are amazing animals, but they are not suited as pets for children. As prey animals, they are timid, sometimes defensive, and an be aggressive as a result. They need to be respected and given the chance to come to you, rather than being picked up and petted and played with on demand. My children, for example, despite being interested in our rabbits, cannot be trusted with them, and so they are my pets. If you want the rabbit for your own sake, wonderful. If you have older children, they may enjoy each others company. If you have young children, be prepared to keep your children separate from your rabbit. They can live for 12 years or so. I don't know how old this rabbit is, but consider lifespan, also. It's a big commitment, and as they age, medical bills can rise (and most treatment isn't covered by insurance for rabbits). If you can rehome a rabbit that is a wonderful thing, but before you make a commitment or spend money on housing, please make sure it's not a decision you will regret. (The fact that you've asked for advice on here suggests that you are an ideal bunny owner though!).
Good luck.